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Beneath the Earth

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"All the roots hang down, swing from town to town
They are marching around down under your boots
All the trucks unload beyond the gopher holes
There's a world going on underground."

A very short distance beneath our feet, there dwell fantastic beings, societies and terrors.

Those who live Beneath the Earth are often exiles from the World Above. They fled either to create a new home for themselves, or to harbor their grudge for revenge (depending on how well they did). Alternately, they may have fled to escape The End of Their World as They Knew It. If they had better technology or more resources, they might have built an Elaborate Underground Base or even an Underground City, but if they don't, they have to make do with simple caves and tunnels.

The urban area version of this trope is a remarkably livable sewer system. Sewers are surprisingly clean and warm, relatively speaking, with good lighting and electricity access. Maintenance crews never stumble across the living quarters, nor do power companies realize the drain. (Sewer Dwellers don't pay electricity bills.) Other times, the ruins of an older city may be paved over when a new one is built, leaving the remnants of old streets and buildings to form an under-city home to surviving stragglers, giant vermin, and assorted eccentrics. New York has an especially crowded sewer system.

Go a few kilometers deeper, and the Earth's crust is filled with spacious caverns. The really lucky underground dwellers will have a Lost World thing going, with flora and fauna in abundance (although occasionally with monsters like Living Dinosaurs). If this subterranean landscape is so vast and habitable that it effectively has a sky, it qualifies as a Hollow World.

Not so lucky ones (who often want revenge on whoever forced them to live here) get gloom, fungus (often of incredible size and possibly sentient) and lava (which tends to be somehow survivable). Often based on The Morlocks in H. G. Wells' book The Time Machine. Particularly well-to-do ones will build an Underground City instead.

In mythology, folklore, and fantasy, this is typically where you'll find The Underworld. (Or that other place.) In Science Fiction and pulp settings, this will often be home to the Mole Men or dinosaurs in a Lost World. In fantasy, expect instead to find dwarves, goblins, dark elves and Bat People making their homes down here. In either case, Big Creepy-Crawlies are a common part of the local fauna. Subterranean civilizations armed with giant Robeasts are a common Super Robot Genre antagonist. The King in the Mountain can also be found here, resting until his hour of need comes again.

The urban version often overlaps with Absurdly-Spacious Sewer. In video games, this is a common location for an Underground Level. When there's a whole hidden social system living underground, in secret but fairly regular contact with the mundane surface population, that's a Wainscot Society. See also Mouse World, which is basically this but on a smaller scale; Dug Too Deep, for when delving into these places releases something horrible; and Hollow World, for when the entire planet as we know it is basically a shell wrapped around a closed-curve version of Beneath the Earth.


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    Anime and Manga 
  • The Mysterious Cities of Gold: The Morlock-like Olmecs dwell in underground cities.
  • Sgt. Frog gives us "Side 6", an underground city which functions as home and refuge for all alien immigrants on Earth. Apart from being underground, it looks exactly like any other street in Tokyo, with Expies of known locations like Akihabara.
  • Texhnolyze: The city of Lux is underground. The ancestors of its inhabitants were banished there.
  • Uzumaki: There is an Underground City located beneath the town of Kurozu-cho that seems to be the source of the spiral curse.

    Comic Books 
  • Judge Dredd: Mega-City One was built right on top of the old cities of the eastern United States, which have since become the Undercity, an inhospitable area now housing feral mutants and various other nasties. It's so dangerous that it's sometimes chosen as an alternative to exile in the Cursed Earth by Judges who take the Long Walk.
  • Justice Society of America has the realm of the Diamond Men, who break out and invade Civic City.
  • X-Men: The Morlocks, mutants who can't pass for normal humans, live in the sewers. Originally they chose to have their physical appearance altered by Masque as a sign that they had rejected the surface world.

    Fan Works 
  • Child of the Storm:
    • As in real life, the Catacombs of Paris a.k.a. the City of the Dead, exist and make an appearance in the first book — here, as the temporary lair of Gravemoss. Being an ancient and thoroughly evil necromancer, he feels right at home... right up until Harry Dresden's Death Curse (he got better) blasts him halfway to orbit.
    • The canonical example of Chicago's Undertown from The Dresden Files is present here; as per canon, it's a product of the fact that Chicago's swampland location means that bits of it periodically sank into the surrounding land, and bits have been built on top. It's home to a number of unpleasant supernatural creatures, its geography frequently changes, and, naturally, a young Bruce Wayne tried to sneak down there because he was curious.
    • There are remains of a rather large and downright ancient fortress underneath an island in the Hogwarts Lake, which serves as the setting for the altered First Task. No one's entirely sure when it was built, but it's largely empty — unless you count the mutated Grindylows. Or so it appears... what with the utterly ancient Elder Wyrm, a planet-killing dragon that routinely eats intruders or enslaves them as wights (in its sleep). And unfortunately, it decides that with Harry's appearance, it's finally got something worth waking up for.
  • The Keys Stand Alone: Or, beneath the surface of the Flying Island of Tipaan in The Soft World. Most of the Svenjaya have to live in the Svenjaya tunnels. The tunnels play a key role in the Tipaan chapters.

    Films — Animated 
  • An American Tail: The Treasure of Manhattan Island: The exiled tribe of Native American mice (though this also crosses over with caverns, being that there is a system of small mouse-sized caves beneath the New York subway system in which the tribe dwells).
  • Children Who Chase Lost Voices: The land of Agartha is underground and can be reached only through certain well-guarded entrances. It is a complete Hollow World, with some sun-like source of light (but no stars) and its own megafauna. However, its inhabitants are very xenophobic due to their previous experiences with surface-dwellers.

    Films — Live-Action 
  • Beneath the Planet of the Apes has one that combines urban and caverns. The humans who escaped the fall of civilization thousands of years earlier retreated to buried New York City and, due to living next to a giant nuclear warhead, they became mutant, telepathic humans by the time Taylor and the rest arrived.
  • Billy Club (2013): Alison finds an underground bunker by the lake near Coach Fredericks' cabin. In it, she finds more etchings in the walls of Billy's bat, and Coach Fredericks' skeleton.
  • C.H.U.D.: The sewer-dwelling hoboes mutated into the titular Cannibalistic Humanoid Underground Dwellers.
  • Dark Heritage: The descendants of the Dansens have dug tunnels that radiate out from the mansion, and which serve as dwelling places and routes of travel for the feral descendants.
  • Demolition Man: The anarchist/rebel types led by Dennis Leary's character live in tunnels beneath the city of San Angeles.
  • Metropolis: The rich live in a bright shiny modern city, and the workers live in dreary underground apartments accessed by huge elevators crammed full of people at the end of each shift.
  • Marebito: A man obsessed with fear finds his way into a warped underground labyrinth world and rescues a feral girl who turns out to be a vampire.
  • The Matrix: Zion, Humanity's last civilization free of the Matrix, is located underground and powered by geothermal energy.
  • Redwood Massacre Annihilation: The base where the killer everyone's looking for is is underground.

  • Fyodor Berezin's Ash 2001: Humanity's only extrasolar colony is nuked in The War of Earthly Aggression, resulting in survivors hiding in an underground city built just prior to the destruction. Other survivors live in a base under the ocean. Earth forces have no idea anyone survived but continue to nuke the surface. The underground survivors are building nukes to retaliate against the enemy base.
  • Beneath sees the protagonists winding up in a colony of people under New York City... whose leader is plotting to one day return to the surface and take over.
  • Dark Cities Underground posits that this trope exists as modern-day fiction's retelling of the myth of Osiris.
  • Discworld notes on several occasions that Ankh-Morpork is a) originally built on loam, and b) thanks to numerous fires and invasions, now mostly built on Ankh-Morpork. This means that there are more layers of buried city beneath the streets than anyone cares to count, and it's quite easy to knock a hole in the cellar wall and find an empty underground street. Even where it's filled up with loam, to dwarves used to mining through bedrock, it's practically a walk in the park to get around.
  • Downsiders: There's a whole community of people who live under New York City in what is really a large extension of the subway system, built in secret.
  • The Dresden Files has Undertown, an area under Chicago full of mildly-radioactive supernatural beasties, explained as being a product of the fact that Chicago is built on a giant swamp, and bits of kept sinking and being built on top of. Oh, and its geography sometimes changes at random. This makes it exceptionally convenient for supernatural creatures that don't like daylight, which is largely why Dresden avoids it like the plague. The radioactivity part comes from the fact that the Manhattan Project was apparently under there — briefly. Separately, there's also the endless Eldritch Abomination prison extending under Demonreach.
  • The Iron Teeth: Blacknail was born in tunnels beneath a human city. His tribe used to live there for generations. A large monster-filled network of caves called the Deep has also been mentioned, but only briefly explored. Small insects called Harvesters live there and build vast mushroom farms.
  • "The Machine Stops": Humanity lives in underground complexes, as the surface air is cold and poisonous. Or at least that's the official story.
  • The Penultimate Truth: Common wartime workers live and work in underground "ant tanks" while armed robots fight on a fatally irradiated surface. One of them, Nicholas St. James, is sent to the surface and learns that the war has been over for years and its engineers have kept them below surface in order to take the land for themselves.
  • The Relic centers around a monster living in the tunnels beneath a museum, and its sequel Reliquary had mutants dwelling in the deepest parts of New York's sewers.
  • Rivers of London features the Quiet People, descendants of the diggers on London's underground and sewer systems, who never returned to the surface and have become a kind of Fair Folk.
  • Shadowmarch: Funderlings designed and built entire town beneath the Southmarch castle, as well as labyrinth of caverns and tunnels beneath it. Similar subsurface Funderling town exist beneath Syan, and there are probably other beneath various cities through Eion.
  • Star Wars Legends: There are Coruscant and Taris, and any other city-planets or very large cities that get mentioned. The rich live at the tops of skyscrapers, while the poor live much lower down in those skyscrapers, in slums crushed under the weight of and with the sun blocked out by said skyscrapers. And then there are the outcasts, who live either in caves, sub-sub-sub-basements, or the Absurdly-Spacious Sewer systems required by such large populations.
  • The War of the Worlds (1898): Discussed when the artilleryman briefly involves the hero in a plan to form an underground resistance movement against the Martians based in the London sewers (which, he says, would be swept clean by the rain once they've fallen into disuse), using tunnels connected to cellars throughout the city. Nothing, besides a single half-dug trench, actually comes of his plan.

    Live-Action TV 
  • The 100: The Mountain Men live in an enormous underground bunker inside Mount Weather, as the radiation levels on the surface are lethal for them.
  • Angel has Angel and company stumbling onto a community of sewer-dwelling kids after Jasmine takes over the outside world. Not to mention the Buffyverse has all the demons, vampires, ect, that live down there.
  • Beauty and the Beast (1987) featured "the World Below", an elaborately gothic underground colony secretly constructed long ago and connected with the sewers and subways of New York.
  • Bones: In "The Woman in the Tunnel", Brennan and Booth investigate the murder of a woman who was doing a documentary about an underground society under Washington D.C. Brennan finds the society fascinating.
    Dr. Brennan: Every society has its bottom-dwellers, and every society fears its bottom-dwellers, because they are a symbol of what happens in that society if you fail.
  • CSI: NY: The Compass Killer is tracked to his hiding place in a forgotten underground apartment beneath a park in Queens, and pursued through adjoining storm drains and sewer tunnels.
  • Neverwhere takes place in an elaborate underground society beneath the streets of London. There's definite magic in the setting, and some hints that the lower chunks of the system aren't really connected to the "real" world.

    Tabletop Games 
  • Esoteric Enterprises: A major part of the setting is that just about every city has an Undercity, usually a mix of expanded sewer systems, natural caverns and other underground facilities. The Undercity is inhabited by various criminal and occult factions vying for power, and is a perfect way to justify a modern-day dungeon crawl for the player characters
  • Old World of Darkness: Several games incorporate this trope. Vampire: The Masquerade has Nosferatu warrens, which the deformed vampires dig out among the basements and sewers of human cities, while Werewolf: The Apocalypse has Black Spiral Dancer hives.
  • Pathfinder:
    • When Magnimar was built, the man contracted to build its sewer system was secretly a high-ranking priest of the god of thieves, and built the city's underground with this trope firmly in mind. As such, Magnimar lies above a complex system of tunnels, passageways and secret hideouts connected to the actual sewer system and the city's basements. It's mainly home to the city's thieves' guilds, in addition to small bands of sewer goblins and the usual menagerie of giant insects and oozes.
    • The crusader city of Kenabres is built over a system of Absurdly Spacious Sewers, catacombs, tunnels and bunkers built over and out of a preexisting cave network. The Kenabres catacombs were built in haste and are poorly mapped, and have over time become home to pariahs, criminals and a large population of mongrelmen — Beast Men with the features of several animals at once — descended from people mutated by the influence of the demons of the Worldwound that Kenabres' crusaders struggle to hold back.
  • Shadowrun:
    • The Seattle Underground, a real-world complex of abandoned and buried buildings from the 19th century, has been colonized by orks and trolls as a cross between this trope and an ethnic neighborhood.
    • Thousands of years earlier in the same verse, artificial underground cities called kaers provided shelter for Earthdawn's inhabitants during the time of the Horrors.
  • Underworld 2000 has a setting and flavor similar to that of Neverwhere, but set under New York City instead of London.

    Video Games 
  • In Asteroid 5251, Gladsbury's citizens lived beneath the earth under an artificial sun for thousands of years.
  • Astroneer: All planets and moons have extensive, multi-layer cave networks, full of dangerous plants and valuable resources.
  • Bloodborne: The Chalice Dungeons are located deep underground beneath the city of Yharnam, which also has an intricate layer of sewers and storage tunnels underneath it as well. Ailing Loran in particular appears to be built into the sides of an enormous desert canyon.
  • City of Heroes:
    • The titular city has an impressively large, intricate, cavernous, and heavily-populated sewer system. If heading down there, expect zombies, evil cultists, devil-worshippers, Nazis (until they got RetConned out, anyway) and cyborgs. If you head deeper into the Abandoned Sewer System, you'd better bring friends, since it's virtually covered with interdimensional mutants, hostile aliens, demons, ghosts, and the occasional tentacled superdimensional monster-of-the-week.
    • The "lost city of Oranbega", archaic and arcane ruins teeming with the Circle of Thorns and their summoned behemoths which lies beneath even the sewers.
  • EarthBound (1994): Most of the ROM Hack Unearthed takes place underground, with several locations having underground villages with their own species and ecosystems. You do go to the surface on occasion, but it's often for minor things such as getting items.
  • Fallout: New Vegas: The Tunnelers in Lonesome Road resulted from the mutation of the Divide's residents who took shelter underground during the Great War. The second nuclear catastrophe, triggered by the Courier, released them to the surface.
  • Final Fantasy XII: After Archadia invades Dalmasca and takes over Rabanastre, the city's inhabitants are forced to live in the underground tunnels formerly used for storage of goods and merchandise. Only the extremely wealthy Dalmascans live on the surface.
  • Gears of War: The Locust Horde lives underground. The day that they began their war against humanity is referred to as "Emergence Day" due to them bursting up out of the ground.
  • Metro 2033 features the post-apocalyptic variant, with a small civilization of humans clashing in the depths of the Moscow underground railway after a devastating global nuclear war.
  • Project Eden takes place almost entirely under a futuristic megacity. It's not all sewers, either — a lot of the game area once was inhabited, or part of massive maintenance systems and factories. Some neutral characters still live down there... along with a lot of hostile ones.
  • Sheltered is mainly set in an underground bunker that the family is living in in the post-apocalyptic Earth.
  • ThanksKilling Day: the kid finds a large underground facility underneath his family's farm when he falls through the floor in the tool shed that opened underneath his mother.

  • Dragon City: Some dragon cities are built beneath various human cities (such as Dragon City New York). Most sewer workers in those cities know about the dragons.
  • Girl Genius: Paris has large sections of its population living in elaborate catacombs and cave networks underground, and Mechanicsburg likewise lies above a complex, multi-layered system of tunnels, basements, and secret chambers. Most cities have underground networks of this sort, although most aren't as extensive — if they did, Europe would be one hard rain away from collapsing in itself.
  • Sluggy Freelance: The tunnels beneath Kesandru House (or where it once stood) were originally just a squat stretch of bare earth that Bun-Bun hung out in. But then the Dig-Bots (tiny, self-replicating robots designed to improve the living space) got to work. Eventually they built their own night club down there, and their own mall.

    Web Original 
  • Looming Gaia: In Damijana's sewers under the Shadow Sector live a society of vagrants, who call it the "Gutter Sector".
  • Mahu: In "Second Chance" the fleeing people of Earth appear on a new planet covered in ice and snow. The surface makes like difficult, if not impossible for normal humans, so most of them choose to inhabit and create expanding cities underground.
  • Welcome to Night Vale: Night Vale's Desert Flower Bowling Alley and Arcade Fun Complex is purported to contain a vast underground city beneath the pin-retrieval area of lane five. However, expectations are confounded when it turns out the city beneath Night Vale is actually a miniature metropolis. Unfortunately, its citizens are still quite dangerous, as Carlos finds out to his peril.

    Western Animation 
  • Downtown: Fruity, Matt and Chaka venture into the subway tunnels in New York so Matt can tag the trains; while they wander around, they talk about all the crazy inhabitants they've heard tell of. Suggestions include: survivalists, mole people, giant snakes, and transit cops who stage fights.
  • Futurama: The ruins of New York were simply paved over, and still exists in disrepair beneath the streets of New New York. They connect to an extensive sewer system, where a civilization of sewer mutants lives in shantytowns and scavenges stuff that people flush down the toilet. They have their own sewer system down there, complete with rumors of sub-sewer mutants living in it.
  • Gargoyles: A community of homeless lives underground. The Labyrinth Clan, humans mutated into feline-gargoyle creatures, became their sworn protectors since they could not return to their old lives.
  • The Simpsons:
    • "The City of New York vs. Homer Simpson": When Homer tells the story of his first trip to New York, it culminates in him falling down an open manhole and being attacked by C.H.U.D.s.
      Homer: ...and that's when the C.H.U.D.s came at me.
      Marge: Of course you'll have a bad impression of New York if you only focus on the pimps and the C.H.U.D.s.
    • "Hello Gutter, Hello Fadder": Parodied when the sewers beneath Springfield contain Morlocks, C.H.U.D.s and Mole People (led by Hans Moleman).
      Moleman: There is no escape from the Fortress of the Moles!
      [Otto/Homer's bungie cord retracts, pulling them upward]
      Moleman: Well, except that.
  • Teenage Mutant Ninja Turtles: The turtles live in New York's sewer system, and a fair few villains have made their lairs in the improbably spacious sewer system as well.

    Real Life 
  • About 20,000 people live in the kilometers of tunnels under Sofia, Bulgaria, most of them homeless or criminals.
  • There were so many catacombs, caverns, tunnels and quarries dug out beneath Rome and Paris that the ground is like swiss cheese. (buildings began falling into the ground) and had to be filled in with artfully stacked rubble made of the bones of millions of plague victims. Rome's catacombs were reputedly inhabited by persecuted Christians. Easy access to limestone bedrock, which could be quarried and burned to produce mortar and fuel, is probably why these cities grew so large in ancient times. The extensive network in Rome is such that it seriously impedes construction of the city's Metro.
  • Watch Cities of the Underworld on History channel.
  • Many, many people live underground in Paris, Rome, New York, and possibly other major cities. They range from the occasional traveler (mostly the case in Paris) to the homeless (the case in New York)
    • In 2003, the French police found a 400 square meter cinema in Paris's underground, fully equiped with electricity, phone, and a small restaurant. The Parisian police even have a dedicated squad patrolling the underground to chase intruders.
  • In 1934, G. Warren Shufelt, working off of a Hopi legend of the Serpent Brothers, went in search of the lost underground city of the lizard people, tunneling a shaft down a thousand feet in downtown LA before eventually giving up.
  • The town of Coober Pedy, Australia. The only reason it exists is because opal was discovered there. During the summer, surface temperatures can reach 50 Degrees centigrade, so the 2000-some residents all live in (quite luxurious) underground houses.
  • The ancient city of Petra, Jordan, carved out of rock. Most of these 'buildings' are only façades. It is thought that the carved out buildings are either tombs, temples, offices etc. Most of the daily activities were going on in the camp on the plain between the mountains.
  • As noted above in the Shadowrun entry, following an enormous fire in 1889 and having a constant battle with tidal flooding, the city of Seattle rebuilt its entire business district one story higher, on top of the mostly filled-in ruins of the first version, leaving a motley collection of privately-owned tunnels, many of which exist to this day; some of them have been cleaned out and host tours.
  • Theme parks such as Disneyland, interlinked museum networks such as the Smithsonian Institute's D.C. facilities, and major hospital or university complexes worldwide tend to have elaborate networks of tunnels, storage facilities, offices and logistics below ground level, where the guests/patients/students never see them.


    Anime and Manga 
  • Getter Robo: The Dinosaur Empire, where evolved dinosaurs were forced to hide underground since Earth was being bathed by a type of cosmic radiation — the Getter rays — that was killing them.
  • Kotetsu Jeeg: The Yamatai Kingdom are a subterranean civilization who attempted conquering Japan in ancients times, but they were defeated and fled underground. Queen Himika harbored a grudge, and longs for revenge.
  • Made in Abyss has the Abyss. Despite the name, it's for the most part well illuminated because of the fluorescent mists that pervade it. The farther down someone travels, the more elaborate its contents become, with upside-down forests, enormous plants, flying serpents, and buried cities existing in the depths. People risk death to retrieve the incredibly valuable artifacts found on the lower Layers, although past a certain point, the Maybe Magic, Maybe Mundane Curse of the Abyss means that return becomes fatal.
  • Maso Kishin Cybuster (loosely on Super Robot Wars) has a world in the middle of the Earth, though this might be a magical dimension.
  • Mazinger Z and Great Mazinger: The Mykene are a civilization that lived and thrived in the Greek island of Bardos millennia ago, using mechanical giants that blast fire from their chests to protect their land from invaders. An earthquake destroyed their island and forced them to seek shelter underground. They lived below the Earth for millennia, building their cities in networks of subterranean tunnels and caverns and grafting their bodies into Humongous Mecha to survive. Unlike other examples from this trope they do not strictly harbor a grudge against humans... but they do not like them, nonetheless.
  • Spider Riders: The Inner World exists deep beneath the surface of the Earth. Two subterranean civilizations live within it — humans, and insectoid people called Insectors.
  • Tengen Toppa Gurren Lagann has a DIY version, with humans living in a labyrinthine system of caves they dug out themselves and thinking of the surface as being just a myth.

    Card Games 
  • Magi-Nation: The Underneath is a large cave system home to a large city and fungus jungles.
  • Yu-Gi-Oh!: The Subterror archetype, in particular the Behemoths, are all depicted as gigantic monsters living underneath the earth. This is emulated with their effects, which involve flipping themselves face-down and then using their abilities when they are flipped face-up.

    Comic Books 
  • Supergirl:
    • In Action Comics #272, Supergirl visits an alien planet called Terra and discovers its center is inhabited by a humanoid civilization.
    • The Untold Story of Argo City reveals that the forbidden caves of the Kryptonian city of Kandor were dug by an ancient race long before the city was built on the surface. Kandorians are forbidden from exploring the caverns because they were bobby-trapped to protect veins and caches of valuable and rare minerals.
    • "The Unknown Legionnaire": While exploring the Protean homeworld, the Legion of Super-Heroes discovers a large underground ghost city, lit up by artificial suns, and built by an alien race known as the Llorn when climatic change rendered the planet's surface inhabitable.
  • Amulet: It's implied that Alledia is actually a sort of alternate Earth, but they definitely get there by going down a very, very long staircase.
  • Disney Mouse and Duck Comics:
    • Disney Ducks Comic Universe: It's revealed in the aptly titled Land Beneath the Ground that the entire Duck Earth is apparently filled with two races, the Terries and the Fermies, with the world they live in being referred to as Terry Fermy by these residents. They are the ones responsible for causing earthquakes.
    • Mickey Mouse Comic Universe: Wing Ding hails from Concavia, a land 5000 miles below the surface. The capital is given the name Procrasta, but if Wing Ding's people have a name, that one is not give. They are at war with the twitz, a 2-dimensional species which can turn invisible by walking sideways. A notable manner of wildlife are smoke-tigers. No explanation is given how anyone got there, which isn't surprising if one considers that "A Fatal Occupation" is inspired by Journey to the Center of the Earth, which also explained nothing.
  • Marvel Universe: There are a number of cavernous underworlds deep beneath Earth. Subterrannea is inhabited by yellow-skinned, weak-willed humanoids and ruled by various humans who've gone there over the centuries — most notably the Mole Man, a Fantastic Four villain. There are also the Lava Men from The Avengers and lots of giant monsters. Supposedly, most of these beings were genetically engineered ages ago by the Deviants, another subterranean race who were themselves genetically engineered by Celestials.
  • The Transformers (Marvel) introduced violent "Mutants" who live deep below Cybertron's surface and make a point of hunting any Cybertronian that enters their domain.
  • Justice Society of America: In one Golden Age story fights the Diamond Men, who live in a realm hidden beneath Civic City.

    Comic Strips 
  • Flash Gordon has the Cavern World of Syk, home of the Blue Magic Kingdom ruled by the Witch Queen Azura. That's beneath Mongo, not Earth.
  • Prince Valiant has the subterranean realm of the Dawn People. One storyline has Val traveling through it to rescue Aleta, encountering monsters and what-not.

    Fairy Tales 
  • "Reygoch": A vast network of caverns, passages and subterranean streams lies beneath Frosten and the endless snowy plain surrounding the ancient city. As exploring the caves, Curlylocks and Reygoch find treasures which had been swallowed by the earth long ago: castles, ships, weapons, buried treasures...
  • In Asbjørnsen and Moe's "The Old Dame and her Hen", the Man o' the Hill lives in a large cavern, full of chambers, corridors and trapdoors, beneath a hill.

    Fan Works 
  • Antipodes: The survivors of Equestria's collapse who were stranded outside of the twilight zone, where the surface eventually became wholly uninhabitable, survived by going underground and hiding in vast bunkers shielded from the extreme elements. Jigsaw and Tiptoe come from one such base on the day side, connected to an immense cave system that it draws its water from. Subterranean networks of this sort are implied to run beneath a great deal of the world, but to be too dangerous to travel through due to the monsters inhabiting them.
  • The Lion King Adventures: In The Lost World, Simba, Nala and Haiba discover an underground world populated with dinosaurs and backwards Wild West lions.
  • Nine Days Down: There is an extensive network of caverns and tunnels beneath the surface of Tartarus, crossed by underground rivers and home to monsters such as predatory shrimp, clans of wights, and unique and dangerous entities sealed in isolated caverns. When he first comes to the surface, Bait the wight is profoundly unnerved by the experience of being in a seemingly endless open space without any walls or ceiling.
  • The Palaververse: An extensive underworld exists beneath Theia's surface, permeating the planet's entire volume down to its core in a maze of tunnels and caverns, underground rivers and plumes of lava rising from seas of magma. The uppermost layers are (relatively) tame and home to the underholds and mines of the Diamond Dogs, but the deeper levels are home to things like sapient colonies of fungi, living patches of darkness or poisonous gas, blind and flightless cave dragons and the Dwellers Below, Eldritch Abominations spawned by primal and chaotic magic. Supposedly, the Diamond Dogs originally lived in the planet's very heart, but migrated upwards to their current location after an apocalyptic "Creation War" between unspecified empires turned the planet’s core into a sea of molten rock.
  • The Unfantastic Adventures of Bizarro No. 1: The Blue-Kryptonite Men live in a network of caverns under the surface of Bizarro World.

    Film — Animated 
  • The Incredibles parodies the tendency for comic book supervillains to come from here with the Underminer at the end of the movie.
    "I am always beneath you, but nothing is beneath me!"

    Film — Live-Action 
  • The Descent: An uncharted cave hosts a group of Gollum-like, blind, stunted little cave people with remarkable agility and bat-like sonar capabilities.
  • Superman And The Mole People: The underground civilization reveals itself when a deep well penetrates the rock around it.
  • The Lord of the Rings: Moria, the subterranean dwelling of the Longbeard Dwarf clan under the Misty Mountains, and now a lightless ruin home to hords of goblins, trolls, and an ancient demon.
  • Star Wars: In The Phantom Menace, the planet Naboo is riddled by a tangle of flooded caverns inhabited by gigantic fish and monstrous leviathans, used by the Gungans, who live in its uppermost reaches, as a swift but risky path through the planet. The humans living on the paradisiacal surface are apparently completely unaware of this, as they happily build their cities and homes along the shorelines of bodies of water that lead directly into the monster-filled abyss.
  • Pitch Black: It's implied that there's a fairly substantial subterranean ecosystem beneath the surface of M6-117, to account for where all the bioraptors came from.

  • Age of Fire has the Lower World, a network of tunnels and cave systems said to be home to most of the surviving dragons. It's often mentioned during the first two books but only rarely and briefly explored. In contrast, most of the third takes place there; it turns out that the Lower World is not only absolutely massive, but may well be just as populous as the Upper.
  • Artemis Fowl: The Earth is permeated by an extensive system of caverns and vertical abysses leading to the planetary core, which the books claim are necessary for allowing magma flares to expend their energy in without tearing the crust and mantle apart. The fairy folk retreated there after being forced away from the surface, and now mostly live in Haven City within a massive cavern.
  • Isaac Asimov:
    • David Starr, Space Ranger: Mr Benson correctly predicts that the Martians have moved underground where they dug a vast network of underground tunnels to retain liquid water and atmosphere. He suspected that the Martians may have been poisoning the Earthmen's crops to get rid of the invasion.
    • "The Secret Sense": Martian civilization exists as cities underneath the surface of the planet. Therefore, Earth couldn't see how technologically advanced its people were until they visited.
  • The Belgariad: The Ulgos have lived in the caves below Ulgoland for centuries. They are featured particularly in Magician's Gambit.
  • Below: Nobody knows who built the Elder Kingdom, a sprawling underground network of cities, mines, and tunnels between them. It was abandoned so long ago that the Romans found it empty of people when they explored, and now only dangerous creatures live there.
  • Bigfoot and Littlefoot: Boone's Sasquatch community lives in Whiddershins Cavern, which is a sizeable cave system big enough for them all to have made it various nooks and crannies into stores, a school, and a residential area.
  • The Books of Ember: The City of Ember is a post-apocalyptic bunker the size of a city that was built inside a colossal natural cave. Leaving it or entering it involves a climb up or down steep natural tunnels and a trip down an underground river.
  • The Chronicles of Narnia: There's a "Deep Realm" beneath the surface of the Flat World ruled by the Lady of the Green Kirtle, but it turns out that her enchanted gnome slaves are actually from an even deeper realm called Bism, where gemstones are alive. Once roused from their enchantment, they find the so-called Deep Realm uncomfortably close to the sky...
  • Cthulhu Mythos: In the 1930 short story "The Mound" written by Zealia Bishop (but ghost-written by none other than H. P. Lovecraft) a Spanish conquistador descends into an underground world of caverns bathed in blue light called K'n-yan. In true Lovecraftian fashion, this world proves only the first of a succession of otherworldly abysses. Below K'n-yan is the grotesque, red-lit world of Yoth and below that is the nightmare realm of the lightless N'Kai.
  • The Descent: Our entire Earth is riddled with this trope, and cannibalistic near-human creatures inhabit the global maze of tunnels.
  • Deltora Quest: Lief, Barda and Jasmine discover the descendants of the Pirrans living on underground islands beneath Deltora.
  • Dinotopia has the World Beneath, a vast system of caverns running beneath most of the island. The dinosaurs hid there to escape the end-cretaceous extinction. Later, refugees from the sunken city of Poseidos hid there to try and restart their factories that built their robotic beast-vehicles, but they failed, abandoning the "strutter-works" and handing over their treasure to the tyrannosaurs for safe passage through the Rainy Basin. Besides vast abandoned complexes and flooded ruins, the World Beneath is also filled with natural wonders, including complex speleothems and caves filled with crystals.
  • A Face Like Glass: Caverna is the size of a kingdom, brimming with Alien Geometries, and may or may not be alive. Where it is located is never explained further than underneath a hill either in or near a desert.
  • Fantastic Mr. Fox: The animals build a labyrinth of caves and tunnels to live in and steal food from the rather nasty human villains.
  • Goblins in the Castle: Goblin Land, or Nilbog as it's properly known, is hidden deep beneath the surface in a cavernous area.
  • In John Hodgman's More Information Than You Require, the Mole Men live here with their hideous steeds and the Trogloditic men. Fortunately for mankind, the Mole Men are relatively nice 18th Century Enlightenment-types.
  • Journey to the Center of the Earth takes place primarily in a complex network of caves beneath the surface of the Earth, accessible through volcanic vents. There's even a subterranean ocean, the Lidenbrock Sea, which fills a single titanic cavern, is lit by constant electrical storms, and is inhabited by Prehistoric Sea Monsters.
  • Kane Series: In "Two Suns Setting" there is the strange cavern system hidden beneath dwarf king Brotemllain's burial cave. It's inhabited by huge, white, blind beasts, including a yard-long white cockroaches, as well as sabretooth tigers.
  • Kringle: The goblins' palace is located underground. They're also condemned to remain underground at the end for all time, only allowed free on Long Night.
  • Land of Oz: In Dorothy and the Wizard in Oz, Dorothy is reunited with the Wizard, and they make a journey through various realms beneath the Earth, before coming back to the surface in Oz.
  • The Lord of the Rings: The ancient Dwarf city of Khazad-dûm was delved deep beneath the Misty Mountains, and since falling into ruin has become a dark underworld home to goblins, trolls and an ancient demon. There are even deeper abysses further down, below even the deepest mines of the dwarves, where nameless things gnaw upon the living rock.
  • Memory, Sorrow, and Thorn heavily utilizes this trope. Not only is the Hayholt, capital of Erkynland, built atop the ruins of the Sithi city of Asu'a, but the entire continent of Osten Ard seems to be riddled with caverns and tunnels, the majority of which were constructed or at least "tamed" by the Dwarrows over countless eons. The Dwarrows use these tunnels to travel from one ancient city to another while remaining completely unobserved by mortals and Sithi alike. The tunnels beneath the Hayholt in particular are a major plot device — The Hero Simon gets lost there no less than three times and they are used by various factions to bypass the castle walls during the final battle. Further, they serve as a metaphor for Simon's Character Development.
  • Richard Sharpe Shaver's mythos revolved around an underground civilization of "deros" — degenerate leftovers of an ancient civilization that once settled the Earth. Using the technology of their forebears, the deros cruelly torment us on the surface, and are responsible for more or less every catastrophe that's ever happened.
  • Septimus Heap: The Darke Halls are a huge, subterranean cavern that forms a Darke realm.
  • The Sister Verse and the Talons of Ruin: The cavernous salt mines beneath Octavia uncover the ruin of a massive labyrinth, home to any travelers unfortunate enough to wander inside, and an Eldritch Abomination that traps people in their dreams while it eats them.
  • Star Trek: In the Rihannsu series, the Romulan/Rihannsu colony world Ysail is famed for its vast Saijja Caverns, a network of caves so vast and deep that they cannot be accurately scanned from orbit and have never been mapped. When the Rihannsu government becomes more oppressive in the later books, most of the Ysailsu retreat to the deepest explored parts of the caves, which become an excellent base for La Résistance.
  • Tailchaser's Song has Vastnir, an underground fortress and extensive tunnel complex in the far north of the world. It's a nightmarish place populated by various mutant cats and enslaved normal cats, run by fallen god Grizraz Hearteater.
  • Tunnels takes place almost entirely in an extensive underworld, with the protagonists moving progressively deeper with each book.
  • The Uncommners: The main setting is Lundinor, a city under London, England. It is one of many secret "undermarts" in the world, where people buy and sell everyday objects made magic due to being imbued with human souls.
  • The Underland Chronicles: The Underland is a vast cave system beneath the eastern coast of North America — its one known entrance is in New York City — whose caverns and winding tunnels are home to entire nations of gigantic rats, bats, cockroaches, spiders and similar animals, alongside white-haired humans with translucent skin who moved down there to escape the Sun's eventual cooling. The Underland is home to many varied environments beyond to expected barren caverns, including volcanic wastes, an underground jungle infested with carnivorous plants, and an underground ocean haunted by Sea Monsters.
  • The Weirdstone of Brisingamen's svart-alfar live beneath the earth, and the protagonists have to spend some time spelunking through abandoned (human) mine workings as well.
  • Whispers Under Ground: Peter Grant discovers an underground colony hidden amongst the Tube networks, the sewers and the illegal teenage raves of London.
  • "The Wings Of Night": Lhin and the other Lunarian ancestors moved under the lunar surface many eons ago, when the moon's atmosphere evaporated away.

    Live-Action TV 
  • Doctor Who:
    • "The Web Planet": Ian meets pale, flightless descendants of the Menopterans, who survived underground for generations since the Zarbi took over the surface of Vortis.
    • "The Hungry Earth"/"Cold Blood": The Silurian city lies in a cavern many miles beneath rural Wales.
  • Farscape: In "Taking the Stone", the characters land on a "royal cemetery planet" where the surface is covered in the graves of deceased royalty and a society of young hippies lives in underground caverns. Moya's crew discovers that the inhabitants are suffering from the effects of radiation which is amplified by the caves. Unlike most examples, the safer thing to do is return to the surface, even with all the graves...
  • The Lord of the Rings: The Rings of Power features Moria in its prime, as a thriving underground kingdom of the Dwarves. The Dwarves digging too deep the caverns under the Misty Mountains for mithril is the primary plot point for them.
  • MythQuest: Alex ventures underneath the Earth and into Hades to rescue Euridice.
  • Ultraman:
    • The original series features the highly advanced civilization of an eyeless Human Subspecies that seeks to conquer their surface kin by enslaving Ultraman and unleashing their own monster named Telesdon.
    • Ultraman Ginga: The Victorians are a subterranean civilization of humans protected by Ultraman Victory and the monster Shepherdon. They dwell in massive caverns with light provided by giant Power Crystals called Victorium. However, when aliens begin to pull Victorium to the surface in a plot to resurrect the Big Bad, the Victorians come into contact with the surface world.
  • The Young Ones: In "Boring", the main characters are all bored out of their skulls. Meanwhile, just below their house, the king of the underground kingdom where nothing boring ever happens laments the fact that he may never meet a boring person.

  • Tom Waits: "Underground" is all about this, with the narrator describing a "big dark town" and its mysterious denizens he's found somewhere deep below the Earth's surface.

    Myths & Religion 
  • In both the ancient Norse and Celtic Mythologies, certain supernatural folk lived underground or within and beneath hills and mountains.
  • During the late 19th Century and early 20th, a number of people became convinced that the Earth was hollow, and inside there was a lush paradise of eight-foot-tall blonde genius-poets who were, in many cases, hermaphrodites, usually supposed to be the perfect ancestors of humans. John Symmes even got some support from Congress to go look around the North Pole for an entry-hole. (John Hodgman covered this in his second book, but he wasn't as far off as you might expect.)
  • African Mythology: According to the San tribe, humans and animals lived in underground caves until the creator Cagn led them to the surface.



    Puppet Shows 
  • Fraggle Rock: The Fraggles live in an elaborate world of caverns, with the entrance in Doc's workshop. Or beneath the lighthouse, in the UK version. In both cases, exactly where the Gorgs' garden is in relation to the human world is completely unexplored, although the events of "Uncle Matt's Discovery" and "Red's Blue Dragon" strongly imply through some otherwise improbable tunnels to places like Australia and a world with a dragon guarding golden apples that holes to Fraggle Rock lead through and to alternate dimensions with no surface-related logic, and the Gorgs probably live in a different dimension from us. It's possible that Fraggle Rock isn't even physically located under Doc's workshop or the Captain's lighthouse, but that the hole is simply another portal.

  • Embers in the Dusk has the Caverns under Dis. Almost as insane to navigate as the Warp, but at least there is a chance to get rewards and loot out of it.

    Tabletop Games 
  • Claim the Sky: Inner Earth is a network of tunnels and caves that includes Azari ruins, a Lost World cavern with Living Dinosaurs, and Mole Men (called "undermen"). One of the caverns lies underneath the Sahara Desert, and multiple entrances are buried in the sand.
  • Dungeons & Dragons: A subterranean world is a common fixture throughout the various settings and editions.
    • Eberron: The underworld is called Khyber after the primordial dragon-god from whose body it was purportedly created. In some early material, Khyber was a world of pitch blackness, ruled by Eldritch Abominations from Xoriat, the realm of madness, where cults of surface-dwellers worshipped the mutagenic energies that emanate from its black crystals. Later changes have reworked it so that while there is a "mundane" underworld, where you find subterranean monsters and kobold settlements, that's mostly the least terrible part of the area, unless you're in the Mror Holds (where those subterranean areas are actively occupied by swarms of aberrations); the real trouble in Khyber comes when you start breaking through into the demiplanes, which allow you to find monstrous forests full of soul-absorbing fruit, citadels of flesh or eyes ruled by Humanoid Abominations, the heart-realms of imprisoned Overlords, vaults full of goblins maintaining the culture of an empire that fell thousands of years ago and other fascinating and/or awful experiences for your adventuring party. Notably, these don't touch the world in predictable ways; Belashyrra's prison-realm can be accessed from both the Shadow Marches and Xen'drik, not because it's that big but because both areas host portals to it.
    • In Forgotten Realms and Greyhawk, it's called the Underdark, and both use it in more or less the same way — a very hostile environment filled with ancient evil races where Everything Is Trying to Kill You, and the traditional home of the Drow.
      • It's far from uncommon for entire cities to exist in the caverns — Forgotten Realms, for instance, has Skullport directly under the city of Waterdeep, where it serves as a trade hub between the surface world and the Underdark proper, and the Garden City of Fluvenilstra, built into the giant mushrooms and other magically enhanced plants that dominate the local landscape and home to a robust population of Mushroom Men.
      • In 4th edition, legend has it that it most large tunnels in it were carved out by the blind, agonized strugglings of Torog, God of Imprisonment and Torture, to escape after he was entombed alive during the Dawn War against the Primordials, smashing through the dimensional walls between the mortal world, the Feywild and the Shadowfell in his efforts.
    • Mystara takes this the whole nine yards and makes the world hollow, lined with pocket societies placed there by the Immortals to preserve ancient cultures and organisms that had gone extinct on the surface. This setting was called, sensibly enough, the Hollow World. The planet's crust between the Hollow World and the surface also had the typical cavernous underworld, inhabited mainly by the shadow elves.
    • Ravenloft dosen't have an underworld that spans the entire setting, but one of the islands in the Mists is built on taking this trope to its most horrible conclusion — Bluetspur, home of the mind flayers. Also, the Arak shadow fey lived in a Beneath the Earth environment before the Shadow Rift appeared, while the domain of Timor relocated to lie underneath that of Paridon.
  • Exalted:
    • Extensive systems of caverns, tunnels and abysses extend beneath much of the Flat World of Creation, and have been used for most of its history as a dumping ground for creatures that its various rulers didn't want to deal with — among other things, failed Primordial experiments, the Primordials' own surviving servants following the Exalted's rebellion, and various monsters during the ages of Exalted rule all wound up down there, and are known collectively as Darkbrood. The Mountain Folk also live in city-states within the caverns, locked in a Forever War against the Darkbroods. This was caused by the Solar Exalted, who grew jealous of them, and forced Autochthon (their maker) to geas them into staying underground unless an Exalted said they could come up. The cavern systems take on elemental aspects when approaching the Elemental Poles much like the surface world does — the Western caves beneath the Great Ocean, for instance, contain a large underground sea, while as one approaches the Pole of Wood the caves become filled with forests of giant mushrooms.
    • The Labyrinth is a particularly nightmarish version of stretching beneath the Underworld. Its appearance can vary significantly from place to place and traveler to traveler, but it consistently manifests as a mazelike warren of tunnels and caverns dotted with bizarre cavern-cities, haunted by spectres and hekatonkhires, and growing steadily more hostile and outlandish the deeper one heads until you eventually find the Neverborn's tomb-bodies.
  • In Nomine: The Catacombs, the domain of David, the Archangel of Stone, are a version of this running beneath Heaven itself. They begin as worked chambers and tunnels, before giving way to natural caves as one heads deeper, and lack the otherwise all-pervasive light that fills Heaven; they remain Heavenly, however, and the darkness promotes calm and contemplation. The deepest reaches are home to beings that rarely if ever come up to Heaven's surface; these include angels, shaped with long limbs, large eyes and pale colors to fit their home, alongside strange insects, blind fish, and bizarre grotesqueries — most of these creatures are the souls of subterranean animals, while a few are prototype animals from the early days of creation or lesser spirits who tend to the caves; some are also angels punished for some transgression, or unique creatures made by David for a specific purpose.
  • Lamentations of the Flame Princess: The expansion Veins of the Earth features an endless labyrinth, the titular Veins, miles below the earth, so deep that light has never touched it and full of things that defy explanation. Treasure is plenty down there, but food and light sources are worth their weight in gold.
  • Mechanical Dream: There are immense systems of caverns and tunnels running beneath the world, many holding full-sized rivers, lakes and oceans.
  • Middle-Earth Role Playing: Moria is given an extensive description, showing it as a layered, complex labyrinth of mines and underground ruins home to tribes of orcs and trolls, flocks of flesh-eating bats, restless undead, and serpentine dragons that shun the light of day, although its depths also hide the treasures of the ancient Dwarves and natural wonders in the deeper caves. The deepest levels of Moria are connected to the Under-Deeps, a lightless realm that has never been explored but which is believed to extend beneath the span of the Misty Mountains and where terrible monsters lurk.
  • Pathfinder: The world beneath is known as the Darklands and draws inspiration from pulp fiction of the early 1900s, such as Edgar Rice Burroughs's Pellucidar. It's divided into three layers:
    • The uppermost layer, Nar-Voth, consists of extremely deep and extensive but otherwise fairly normal caverns (which are often isolated and do not form a continuous network), and is the most familiar layer to the surface-dwellers. While most of it is sparsely populated stony wilderness, it is also home to fairly normal humanoids like goblins, troglodytes and duergar, and some less normal ones like derros, vegepygmies, and mongrelmen.
    • Sekamina, the middle layer, consists of much larger and more thoroughly interconnected caverns and tunnels, extending beneath most of the world’s surface. It is home to more reclusive and dangerous races like the drow and ghouls, who rule true underground empires, alongside monsters such as driders, morlocks and gugs. It has more exotic terrain than Nar-Voth, including fungal forests, volcanic caves and a true subterranean sea.
    • Finally, the deepest level — the Vaults of Orv — is as much a subject of fear and mystery for the people of Nar-Voth and Sekamina as the Darklands as a whole are for surface-dwellers. It consists of massive caverns the size of nations, some dark and others lit by artificial suns or glowing crystals, containing environments such as deserts, rainforests, ruined cities, mountain ranges and a vast subterranean ocean. The Vaults are inhabited by a great variety of monsters, ranging from Living Dinosaurs, dragons, monstrous arthropods and the undead to a variety of unspeakable horrors. They did not form naturally, but were excavated by a powerful earth elemental Precursor race called the Xiomorn to host their evolutionary experiments.
    • The Darklands also extend beneath Tian Xia in the far east, although there they are home to creatures such as oni, the Denizens of Leng, haunted clockworks, Rat Men and cave giants rather than the races of the western Darklands.
  • Space 1889:
    • Luna's surface is barren and lifeless, but a large canyon on its far side gives access to an inhabited inner world. After passing through a series of flooded caverns, an explorer reaches a continent-sized cavern mostly filled with water except for a number of large dry shelves and islands projecting from its sides. These are home to large fungal forests and to the city-states of the Moon Men, who descend from survivors of Vulcan, the long-destroyed fifth planet, that sought refuge inside Luna's depths and have now long forgotten their origins or the nature of the external world.
    • The World Beneath the World is a complex system of caverns and tunnels running beneath the global jungles of Venus. It's formed from the constant growth of planet's vegetation burying older layers of the jungles and swamps beneath newer growth and rotting humus, forming a spongelike system of subterranean cavities supported by the petrified remains of ancient trees. This underworld is home to a complex ecology supported by the constant percolation of organic materials form above, mostly consisting of oversized arthropods, tangled fungal growths and sundry bioluminescent organisms. It's also home to the Gri, eyeless, albino relatives of the Venusian Lizard Folk who have been eking out an existence in the caves for generations and have only sparse contact with their surface relatives and the human colonists. The World Beneath the World does not form a single world-spanning network; most of it consists of solitary caverns and small cave systems, and although complexes as large as Australia exist these are not extremely common. However, some speculate that even deeper caves exist and connect the shallower cave systems to form a titanic underworld, chiefly due to the uniform nature of the various cave systems' fauna.
  • Warhammer:
    • The Dwarfs and Skaven both live primarily underground, and over their histories have created extensive systems of tunnels and underground cities for travel and habitation. The Dwarfs created immense fortress-cities known as Karaks and a subterranean highway system called the Underway, while the Skaven created a rambling, chaotic network of tunnels called the Under-Empire. Both exist primarily beneath the Old World's mountain ranges, although the Under-Empire's tendrils stretch beneath most of the world. The two systems have multiple connections dug in secret by the Skaven, in addition to intersecting various natural cave systems; millennia of wars and cataclysms have also ruined most of the Dwarf cities and tunnels. The result is a continents-spanning maze of tunnels, caverns and lightless ruins infested with tribes of orcs and goblins, trolls, fungus monsters, dragons and worse, all beneath the feet of entirely unsuspecting surface-dwellers.
    • Much deeper abysses are mentioned to exist deep beneath the diggings of Dwarfs and Skaven, hiding enormous blind horrors, vast Blob Monsters and cities of ghoulish things where no light has ever shined. One of these areas is Underworld Sea, a vast labyrinth of flooded caves and tunnels stretching beneath the Dark Elven realm of Naggaroth. It's poorly explored, difficult to navigate, prone to floods and cave-ins and populated by ferocious monsters, and there are rumors that the ruins of a lost civilization exist within its depths.

    Theme Parks 
  • Disney Theme Parks: The Journey to the Center of the Earth attraction at Tokyo DisneySea is based around this concept.

  • BIONICLE: There's a "universe" under the island of Mata Nui. It's not technically underground, being inside of a Humongous Mecha that crashed onto the planet a thousand years ago, but from the perspective of the Matoran...

    Video Games 
  • Age of Wonders has two map layers (Shadow Magic adds a third), with caves allowing access to the Underground level.
  • Arx Fatalis: In the background, the sun died out and most civilizations of the world, in a rare moment of truce, moved underground into a networks of caverns mixed with the old dwarven mines and rebuilt their cities and towns, such as the titular Arx. The entire game takes place underground.
  • Cave Wars: True to form, your resource-management includes ensuring a good mushroom-harvest.
  • City of Heroes: Wherever you don't find sewers you'll find caverns, with entrances in every park and abandoned lot. The caves tend to house either trolls (former humans mutated by exposure to a drug that induces super powers), beings of living stone, or the various groups of evil magicians. Occasional inter-dimensional aliens may be spotted, usually busy redecorating the place into an Elaborate Underground Base. Lampshaded at least once in the intro text to a mission, describing your character wondering how any of the buildings in the city keep standing when the ground below is like Swiss cheese.
  • Cry of Fear: the Hole mostly takes place underground, where Simon wanders dark mine tunnels and strange mazes.
  • Dark Souls: The player spends a lot of time in a variety of underground areas, such as demon-infested lava ruins and the Tomb of the Giants.
  • Deadly Rooms of Death: The majority of the game takes place below the surface. Beethro is exploring King Dugan's 25-level dungeon when he finds passages leading to even deeper dungeons, and eventually to the Rooted Empire, which is actually more advanced than the simple agricultural society above.
  • Dominions: The nation of Agartha is based on this. Initially populated by the native Pale Ones, humanoids that can grow to gigantic size, they begin to die out and are replaced by humans who take to worshiping them as the Ages progress.
  • Dragon Age features the Deep Roads, a vast subterranian network of artificial caverns and passages dug out by the dwarves in the heyday of their civilization. It had once consisted of hundreds of underground cities named "thaigs" and the miles-long tunnels connecting them, but ever since the First Blight, all but two of them have been overrun by the darkspawn. One thaig, Orzammar, is the capital of modern dwarf civilization and is visited in Dragon Age: Origins.
  • Dungeons & Dragons:
    • Baldur's Gate II has the Underdark, a vast subterranean labyrinth covering much of the world.
    • Baldur's Gate III: At the end of the first act, the party heads through the upper layers of the Underdark to reach the next story destination. The path winds through dark caverns hanging above deeper, inaccessible abysses, lit by the faint light of huge glowing mushrooms and home to feuding factions of mushroom people and duergar.
    • Neverwinter Nights: The Underdark is revisited in the Expansion Pack fittingly titled Hordes of the Underdark. Several fan-made NWN modules feature the location prominently, as well: an Underdark essentially identical to the one found in Forgotten Realms forms a bulk of Part Two of A Dance with Rogues, despite its setting being otherwise an original Constructed World.
  • Dwarf Fortress has no fewer than three levels of world-spanning underground cavern systems, home of mushroom forests, tribes of animal people and some very weird and hostile monsters, with each layer getting progressively nastier than the last. Dig down past all three of those, and you'll find a great sea of magma and "semi-molten rock". And beneath that, if you can contrive to get at it, is Hell, which can be surprisingly easy to reach, provided you can find the right veins of mineable rock and have a decidedly casual attitude towards being slaughtered by sheep monsters made of ice.
  • The Elder Scrolls V: Skyrim has Blackreach, a giant cave the size of a small country, housing an ancient Dwemer city complex. This, as well as other Dwemer ruins throughout Skyrim, have largely been taken over by the Falmer, a race of subterranean goblin-like creatures who were once the graceful Snow Elves but were taken in and twisted by the Dwemer when their race was threatened by the invading Nords.
  • Exile takes place in a gargantuan network of underground caverns, stretching for several kilometers in every direction, and varying from huge caves big enough to have their own weather systems, to twisting little mazes of passages, all alike. As the name of the area suggests, the people who live there didn't choose to do so, and, sure enough, the place is littered with fungus, lava, and plenty of gloom. Many surface towns also have monster-infested sewers.
  • Fallen London: The Neath is a vast cavern beneath the Earth's surface, well away from the Sun's light and laws. London was transported under the earth as part of three terms of a Deal with the Devil on the part of Queen Victoria to save Prince Albert's life, and Sunless Sea explores the Unterzee, the vast underground ocean that surrounds London.
  • Final Fantasy IV contains an enormous, open-space underworld, populated by dwarves.
  • Finding Light: The only way to enter Heaven's Door is to find the entrance in the Ambrose Underworld, which also contains Eredor, Deepforge I, a vast cave network, Tiamat's lair, and seas of lava.
  • Gears of War: The Locust live in a vast series of underground caverns known as the Hollow.
  • Grow (and other games by the same creator): Tonties live underground in ant-like colonies with a queen and different kinds of Tonties with their own specialities.
  • Heroes of Might and Magic has cavernous underground levels as a series fixture, sharing many resources and sites you can visit with the surface world, and having unique ones too. There's usually an evil faction that specializes in being there (named Dungeon in several of the games) and other (mostly evil) factions might be more or less at home down there. From map to map, the caverns range from nothing to a vast, sprawling system that has as much open space as the surface world or even more.
  • Knight Bewitched 2: Deepforge I is buried deep underground, and there's an entire world map underground known as the Ambrose Underworld, just like the Underworld of Final Fantasy IV. This takes place before the dungeon, Heaven's Door, raised the lava sea level, so more locations are available than in Finding Light.
  • Legacy of the Wizard: The hero and his family must delve deep into a massive system of caverns and underground ruins to collect the four crowns and the magic sword needed to destroy the dragon Keela.
  • The Legend of Heroes: Trails of Cold Steel IV: It's revealed that the location of the Black Workshop is at one thousand meters below a mountain range that can be seen from the town of Milsante. It's where Rean's held as a prisoner at the climax of Cold Steel III and throughout all of act 1 of IV.
  • The Legend of Zelda:
    • The Legend of Zelda: Oracle of Seasons features the Subrosians, who live in the lava-filled realm of Subrosia underneath Holodrum.
    • The Legend of Zelda: Skyward Sword: The backstory explains how The Dark Times in Hyrule began when a great army of demons emerged from the earth and ravaged the land in their campaign to obtain the Triforce.
    • The Legend of Zelda: Breath of the Wild says that Calamity Ganon emerged from beneath Hyrule Castle a century ago to unleash its genocidal rage upon the land. You end up fighting Ganon in the giant underground Sheikah laboratory where it had presumably been sealed up to that point.
    • The Legend of Zelda: Tears of the Kingdom:
      • Some of the larger surface-world cave systems can be very extensive, forming localized mazes of branching tunnels, side chambers and underground lakes and rivers home to glowing plants and animals, camps of apelike Horriblins, and rich mineral deposits.
      • The Depths are a vast subterranean area spanning most of Hyrule's underbelly that serves as a Dark World. They're home to a much more alien ecosystem than the surface caves, characterized by high monster populations and forests of trees with strange feather-like branches, immense mushrooms, and gigantic fern-like plants. Initially, the Depths are pitch black save for those places you've lit up with Brightbloom seeds, only fully lighting up as you activate Lightroots. There are also lots of monster-controlled mines there that are the main source of Zonaite. This is where Ganondorf was sealed away in the distant past; all the Chasms opening up the Depths to Hyrule's surface are the result of his Gloom bursting forth upon his awakening at the story's beginning.
  • Lost Ember has "moles"note  who live in and around a network of tunnels. When transformed into one, you can also dig your way under obstacles and create your own new tunnels.
  • Master of Orion II has the Subterranean racial trait. Being a tunneling sort means that your colonies can support a greater population, and ten points are added to trooper effectiveness when defending against a ground invasion.
  • Minecraft:
    • In order to get anything done in the game, you need to create labyrinthine tunnels deep underground while mining, which is more or less inevitably going to result in a complex maze of tunnels extending from your base — and you need to burrow quite deep to get to the best ore.
    • Natural caves are procedurally generated like every other landform, and get bigger and more extensive the deeper down you go, together with an increasing likelihood of separate caves having connections with each other. Near-surface caves are fairly small and modest, but the ones near the bottom of the game world can get very big indeed, and are almost always interlinked, resulting in huge underground networks. Naturally, these caves are pitch dark unless you light them up with torches, and as such are crawling with hostile monstersnote . Underground lakes and rivers are also common, as are lakes and waterfalls of lava that provide the only natural light down there.
    • The 1.17 and 1.18 updates, collectively referred to as the Caves & Cliffs update, extensively expand on and add to the caves of Minecraft. In addition to doubling world depth in order to create extra space for caves, an update to the cave generation programming results in much more extensive cave systems generating as a mixture of winding labyrinths of long, thin caverns interspersed with immense caverns. Aquifers can also create large underground bodies of water and lava. Three new cave biomes also generate — dripstone caves, filled with forests of speleothems; lush caves, filled with plant growth and bodies of water and lit by vines with glowing berries; and the deep dark, an area found in deepest areas of the world that's covered in dark Meat Moss, filled with ancient ruins, and haunted by a terrible monster.
  • Myst gradually reveals that the lost city of D'ni is in a five-mile-wide cavern three miles below the surface of the Earth, with a lake of glowing algae that acts as a light source, somewhere beneath a vast stretch of desert in New Mexico note . One game in the series actually permits a virtual exploration of D'ni itself.
  • The New Order Last Days Of Europe: Warlords of the Black League in Omsk can establish a complex metro system designed to protect their population from Nazi German nuclear attacks.
  • Poacher: The subterranean world Derek Badger finds himself trapped in does not only have towering cities inhabited by disembodied spirits, but also beaches and forests, and even a jungle.
  • Quake has a secret level named "The Underearth".
  • A staple of classic Roguelike involves Dungeon Crawling in massive, randomly generated, elaborate and extremely complex dungeons.
  • Tangledeep takes place entirely Beneath the Earth, and the plot of the entire game is to get to the surface. Apparently all civilization lives underground; Tangledeep, an infinite, shifting dungeon, sits between civilization and the exit, explaining why nobody ever really manages to reach the top.
  • Tomb Raider: Nearly every single game will have Lara Croft explore an underground cavern at some point that are filled with traps, water, lava, wild animals, and sometimes a T. rex. While she also explores underground urban areas as well, caves are usually more common in the franchise.
  • Torin's Passage has no less than four separate worlds Beneath the Earth, each one nested inside the other. In the outermost world, being banished to the Lands Below is a form of capital punishment.
  • Touhou Chireiden ~ Subterranean Animism has the underground city Former Hell. It's the place where Hell used to be, but now it serves as the city where Youkai who are hated by other Youkais because of their dangerous abilities live.
  • Turok 2: Seeds of Evil has the Lair of the Blind Ones, whose centuries spent in darkness has rendered them eyeless as well as giving them a lethal sensitivity to sunlight.
  • Ultima: In the fifth game, deep below the surface of Britannia is the Underworld, a wild neverland of linked caverns and river rapids that collapses at the game's end. In Ultima VI you can proceed through the ruins and reach the other side of the flat earth.
  • Ultima Underworld: As the title implies, the games are set in massive network of an underground dungeon.
  • Undertale: As the title suggests, the game takes place entirely underground. The Underground was created a long time ago when humanity won a war against monsterkind and subsequently sealed every single one of them Underground.
  • Vivid Conceptions: Beneath the Earth is where the miniature Bantam civilization dwelled before dinosaurs even existed, and where the game takes place.
  • Warcraft has its share of underground caverns.
    • Azjol-Nerub, the capital of the Nerubian civilization, is a sprawling underground labyrinth that stretches across much of the continent of Northrend. The part where the Nerubians used to live is called the Upper Kingdom, and below that is the Old Kingdom, which consists of even deeper tunnels populated by nameless horrors and one of the Old Gods, which was confirmed to be Yogg-Saron in the Wrath of the Lich King expansion.
    • The first forty-man raid instance in World of Warcraft, Molten Core, is a huge lava-filled cavern located deep under Blackrock Mountain. It's home to elementals, lava giants, core hounds and Ragnaros, the elemental lord of fire.
    • The Undercity, the vast subterranean home base of the Forsaken, built underneath the ruins of another city.
  • Zork features exploration of the Great Underground Empire.

  • Dragon Cities: The dragon cities that aren't in the sewers of human metropoles are built within caverns, much like Dragon City Chicago (before the cave-in), where the webcomic primarily takes place. In fact, this is how dragons escaped the mass extinction that wiped out the dinosaurs.
  • Drowtales: The bulk of Drow civilization consists of a handful of large subterranean city-states within large caverns in an extensive underworld, separated by large stretches of stony wilderness home to isolated outposts, driders, degenerate Drow Mole Men, and the few Dwarf nations the Drow didn't wipe out. It was created alongside the sky world during the first of two apocalyptic wars waged by ancient elves when a substantial piece was broken from one of the moons and fell to earth, with the underworld being, in essence, the cracks in the world that impact caused. At least one section, the Nidavellir, is open to the skynote  but filled with a sea of fog. There's also a second underworld under a different continent from the main one, ruled by its own Drow nation, Hel. It's not a nice place.
  • Everyday Heroes: Hornswoggle and family live in an Absurdly-Spacious Sewer.
  • Sam & Fuzzy: The Underground is a massive, world-spanning set of caves complete with underground cities, roads and small communities. It's home to practically everything supernatural that humanity has ever thought was real, mixed with some sci-fi elements as well like artificial robots.
  • Sluggy Freelance: Most of what is seen of the Dimension of Pain consists of caverns; the mostly canonical "Meanwhile in the Dimension of Pain" guest strips confirm that there is a surface above them.
  • Tower of God: Twenty-Fifth Bam was trapped for years inside an underground cavern before the plot started.
  • Woo Hoo features a vast Subterrain, a network of caverns, subways and urban areas, formed when a section of the city sank underground during an earthquake.

    Web Original 
  • Codex Inversus: The Principality of Dis is built atop the ruins of Tartarus, one of the primary areas of Hell before the Collapse. In the World Before, it was a cosmic prison of labyrinthine, shifting tunnels that held dangerous rebels against the cosmic order; in the modern day, its ruin is a sprawling, mostly unmapped cave system prone to shifts as new passages open and older ones collapse. Its depths are home to groves of giant fungi, bizarre ecosystems supported by natural concentrations of mana, treasure troves of pre-Collapse wealth, and the remains of ancient giants, demigods and sinners, all of which draw explorers to plumb the abysses — but, just as often, terrible monsters emerge from the unknown depths of Tartarus to ravage the surface world.
  • The Crew of the Copper-Colored Cupids: The Worlds Below, a network of magical caves beneath the Prime Earth, which include such things as the cavern where Loki is bound, appear in the story The Winter Quests.
  • Crossing Kevin's Crossing: It is rumored that none of the building have basements because of "tunnels beneath the ground and weird people that live there".
  • Dreamscape: CHEN normally resides in the center of the planet.
  • Looming Gaia: Most of Lamai Nation lives in massive underground labyrinths. Any citizens who need sunlight have to go to special sunroof rooms to "worship" the sun every day.
  • Mystery Flesh Pit National Park: The Flesh Pit is both this and a Womb Level.
  • Taerel Setting: Many kin'toni clans have made a permanent home underground, such as the Wialshy Kin'toni Clan, living in the Anyeri Hard Rock Erosional Caves, the Minemi Kin'toni Clan, living in the Ghar Anaroth Caves and the Diwarale Kin'toni Clan, living in the caves of Caldar Mountain. A zu'aan group that lives underground is the Muvon City Zu'aan, who live in the Frib-kada Caves.
  • Orion's Arm: Many worlds have extensive underworlds, either artificial or natural, which are often populated by fairly large societies.
    • Cenote was covered by extensive layers of calcareous stone by a now-extinct biosphere, and over millions of years its waters eroded immense systems of flooded caverns larger and more extensive than any other natural cave system in the known galaxy. Its original colonists opted to take aquatic forms to best explore this flooded underworld and spent thousands of years mapping out its global cave systems. These included caves large enough to build cities in, as well as some dry caves filled with extremely large stalactites, calcite crystals and similar formations.
    • Mercury is a particularly notable example; over its long history, extensive mining activities left global mazes of tunnels and caves, some very large, running through its crust and upper mantle, while later megaprojects added two layers of habitable space above its original surface. Beneath the planet's uppermost surface, modeled to resemble the original Mercurian environment and mostly home to mobile cities, the depths are currently divided into five layers:
      • The topmost, Undervale, is a continuous layer pressurized and terraformed to resemble Mars, and mostly inhabited by colonists from the red planet itself and some others adapted to similar conditions.
      • Next down is Mercury's original surface, called Elderdasht. This has itself been returned to the planet's original state, with the exception of the original settlers' cities which are now encased in Earth-like environments.
      • Below comes Wotum, an agricultural layers with light arrays and a simulated sky on its roof and artificial rain. It's used to grow food for the rest of the planet, including both natural, genetically engineered and nanotech crops.
      • Khazad-dum is a series of distinct, regularly-shaped caverns extending in a geometric pattern beneath the whole planet. They're kept unlit and are home to a large population of sapient robots that constantly demolish and rebuild the empty cityscapes that fill it, alongside small communities of biological sapients that inhabit lighted islands in the middle of the dark emptiness.
      • The lowest layer, Bism, consist of a number of large, interconnected cavern systems expanded from the ones dug by original mining operations. These are kept lit by luminous plants or fungi, or by lakes filled with bioluminescent microorganisms. Its settlements include Stalactitopolis, a city hanging from the ceiling of a large cavern and above one of the glowing lakes.
  • SCP Foundation: SCP-2622 claims to be from a subterranean world straight out of pulp fiction, home to a civilization of Mole Men, evil reptilian people, and caverns full of prehistoric life. He's making everything up.
  • Homestar Runner: In the Strong Bad Email "buried", Strong Bad tries to determine what is buried beneath his backyard kingdom of Strong Badia, mistaking a beer bottle cap for evidence of a civilization of Ancient Astronauts. At the end of the cartoon, you can see a drawing he did showing what might be under Strong Badia, including a "nougat layer", the ancient alien colony of Coldonesdry, and a "dinosaur n sleestak layer".

    Western Animation 
  • Avatar: The Last Airbender:
    • The Earth Kingdom's capital of Ba Sing Se was once a subterranean city built within crystal catacombs carved out by Earthbenders. Following expansion, the caverns were abandoned and the lost city is now know as Old Ba Sing Se.
    • The Fire Nation capital (built in the caldera of a dormant volcano) also has a series of underground tunnels, which are mainly used as a defense bunker in case of emergencies.
  • Chip 'n Dale: Rescue Rangers: The leprechauns live in underground places, which in the case of the leprechaun king Darby Spree can be pretty spacey.
  • Mighty Max: Skull Mountain, located deep underground and surrounded by magma, which is Skullmaster's abode, having been banished there thousands of years ago.
  • My Little Pony:
    • My Little Pony 'n Friends:
      • "Mish Mash Melee": The gnome-like Dell Dwellers live in a system of spacious caves beneath the Mystificent Forest, where they handcraft natural objects to then be seeded in the surface world.
      • "The Quest of the Princess Ponies": The Kingdom of the Lava Demons is a large network of caverns and tunnels beneath the Crystal Desert, most of them containing pools and rivers of molten rock.
    • My Little Pony: Friendship Is Magic:
      • "A Dog and Pony Show": The Diamond Dogs are a group of subterranean dog-men who inhabit a labyrinthine system of tunnels and large caves.
      • In later seasons, Rarity usually goes gem hunting in a long tunnel studded with giant gems. In "Rock Solid Friendship", it's revealed that there's a large cave filled with plant life and lit by a cluster of giant Glowing Gems connecting to it, where Maud sets up her home. In "Uncommon Bond", it's further shown that this cave connects to several mazelike tunnels and beyond that the cave of the mirror pool, ultimately forming a fairly extensive system of interconnected caves running beneath the outskirts of Ponyville and the Everfree Forest.
  • Ned's Newt has trolls living beneath the Earth's surface, who sometimes try to Take Over the World, only to be stymied by the protagonists.
  • The New Adventures of Superman: In "The Neolithic Nightmare", Jimmy Olsen falls into an underground pocket populated by malevolent creatures, including dragons, rocs, and giant spiders.
  • Regular Show: The Carlocks live in caverns that extend from the park's crash pit and subsist on whatever is thrown into the pit, mostly food left in the busted up old cars.
  • Star Wars: The Clone Wars:
    • "Mercy Mission": R2 and 3PO end up wandering about the cave system beneath the surface of planet Aleen. There they encountered the inhabitants, who included tree-like humanoids and the frog-like fairy Orphne, were causing earthquakes, trying to seal the breach between them and the surface, because surface air was poisonous to them.
    • "Bounty": Asajj Ventress and Boba Fett's crew visit the planet Quarzite, whose highly pressurized and storm-wracked atmosphere forces its two native species, the Belugans and Kages, to live in a vast cavern system illuminated by glowing crystals.
  • The Tick: The Mole People are actually a peaceful but weird group who don't want to conquer the surface world, but to just take a vacation. The Lava Men on the other hand...
  • Trollhunters: Trolls originate from deep within the Earth, just as humans come from the surface. Because most Trolls species turn to stone when in contact with daylight, Trolls usually dwell in vast caverns and other underground spaces.

    Real Life 
  • Deep caverns permeated by sulfur gases are one of the major refuges for Archaea, ancient prokaryotes that dominated the primordial Earth before oxygen levels rose in the atmosphere. A far cry from dinosaurs, but still a "lost world" ecosystem that persists underground, billions of years after being displaced from much of the planet's surface. Not just Archaea live there, either. Recent discoveries suggest that an entire "dark biosphere" exists within all areas of the planet's subsurface that aren't so deep as to be magmatic. Everywhere scientists have probed, they find at least a few hardy prokaryotes eking out a living via chemosynthetic metabolism. If there's pores or cracks in the bedrock and so much as a hint of water available, something's gonna grow there, even if it's so hard up for resources that it can only engage in cell division once every millennium or so.
  • Karst topography, formed by water slowly eroding through soluble bedrock over long periods of time, tends to produce impressively extensive cave systems. The largest and most well-known of such caves is probably the Mammoth -- Flint Ridge Cave System in Kentucky. As of 2022, cavers exploring this complex had mapped over 420 miles of chambers and passageways.
  • In Tunisia, there exist the cave homes in Matmama, Tataouine (that the planet was named for) and other desert settlements, where the Berber homes are carved out of the rock to give the locals a cool place to live. Many of these were used for the filming of Mos Eisley and Mos Espa in Star Wars.
  • It was a very widespread belief among Greek and Roman philosophers and naturalists that there were great caverns, abysses and channels running throughout the depths of the earth, containing rivers, swampy morasses and great lakes and seas. This was in part an attempt to explain how rivers could spring out of seemingly solid rock and where they went when they vanished into caves and partly to explain the origins of earthquakes and volcanic eruptions — most accounts of these events tended to assume that they were caused by violent underground storms, floods or turbulences shaking the foundations of the earth, masses of gases or underground fires bursting through the surface, or caverns collapsing into themselves.