This used to be part of a sprawling metropolis, or maybe it was a whole city of its own, but something happened. Maybe an earthquake buried it, or maybe they just decided to build new city on top of it and in time forgot the old one.
This isn't just any underground system
, it must have been a real city at some point. Related to Ghost City
and sometimes Absurdly-Spacious Sewer
Anime and Manga
- In the first anime of Fullmetal Alchemist, there is a hidden city under central that has been destroyed in order to create a philosophers stone.
- Berserk has a massive prison tower built on the ruins of an older city.
- Star Wars has Coruscant, where the ground is always buried under at least five layers of ancient skyscrapers.
- The Undertown in The Dresden Files is located under Chicago, consisting of old buildings that sank into the ground under their own weight. It is populated by various supernatural nasties.
- Neil Gaiman's Neverwhere has a London Below which consists largely of places buried and forgotten by London Above.
- I think Ankh-Morpork from Discworld has this. I think it's said something like "you can travel from one place of the town to another just by breaking the walls".
- To expand on Ankh-Morpork: because the city is built on soft loam, near an extremely turgid river, the ground levels of its buildings find themselves buried every generation or so. The standard remedy is to just build another level on top, so now the city descends through the earth to an unknown depth. This has caused friction between the Dwarfs, who traditionally view anything underground as theirs, and the city's government, who think of those areas as sub-sub-basements and would rather not have unknown factors tunneling through them.
- Also from Discworld, the mine-city of the Low King of the Dwarfs is built mostly under the surface town of Bonk.
- Inverted in C. S. Lewis's The Silver Chair. The thriving kingdom of the Lady of the Green Kirtle is underneath the ruined city of the giants. And there's an even deeper land beneath her kingdom, which is abandoned but not for long.
- Cities of the Underworld is a documentary series that aired on the History Channel and explored subterranean structures under various cities and historic sites around the world.
- Dungeons & Dragons. Judges Guild module Dark Tower. In the Back Story, a small village grew up around the White Tower of Mitra. When the Black Tower of Set appeared nearby, the village was buried by the landslides caused by the battle between the two towers. Within a decade a new village of treasure seekers called Mitras's Fist was established on the ground where the old village had stood. When the new villagers began digging down to find the old village, imagine their surprise when they found someone digging up to meet them...
- Cities in Warhammer 40,000 almost invariably have such an "undercity". They're considered the natural consequence of being established for as long as any WH40K city.
- Forgotten Realms has cities built this way, particularly big and old ones like Westgate. In another way, Waterdeep stands on the still active Undermountain complex and Skullport city and Ravens Bluff stands above an abandoned dwarven city under which there's in turn an abandoned drow city.
- Metru Nui in BIONICLE, under the island of Mata Nui.
- Old Mournhold in The Elder Scrolls 3: Tribunal.
- Saints Row 2 has Old Stilwater, an earthquake-ruined underground district from approximately 1940-1965, inhabited by hobos, accessed by entering the old mission house.
- The Undercity in Baldur's Gate is an ancient settlement located in a cave underneath the eponymous city. It is apparently big enough to house an enormous temple of Bhaal and many supporting structures.
- Paper Mario: The Thousand-Year Door has the ancient city buried under Rogueport.
- The Lost City in Thief game series.
- Wonder City in Batman: Arkham City.
- Blackreach in The Elder Scrolls V: Skyrim, former capital of the Dwarven lands.
- Vagrant Story has an Undercity area, notable for its high density population of undead.
- In Pokémon Colosseum, there is another city buried underneath Pyrite Town, known simply as "The Under". It is actually a full city (complete with shops, an inn, and fighting arena), rather than being just abandoned ruins and buildings.
- Moscow has a lot of Soviet-era underground works, partly civilian (Metro) but mostly of Cold War era Soviet military origin. Urban legends tell about a whole system of special Metro for the government and underground vault-cities in case of a nuclear war, for generals and officers.
- The ruins of ancient Pompeii in Italy buried under whatever the city now on top of it is called. IDK if it's still called Pompeii or not.
- Heck, Rome is like this, and likely many other cities in Europe.
@ Chicagomel: Napoli, (Naples) Italy was constructed on top of the buried ruins of Pompeii.