"One does not simplywalk into Mordor. Its black gates are guarded by more than just orcs. There is evil there that does not sleep, and the Great Eye is ever watchful. It is a barren wasteland, riddled with fire, ash, and dust. The very air you breathe is a poisonous fume. Not with ten thousand men could you do this. It is folly."
The dark twist is that it's still just as inimical to humans as a typical Mordor. After generations of living with pollution, humans can no longer tolerate clean and pristine environments.
In InuYasha, Naraku has a mobile Mordor; a magically generated cloud of poisonous gas that follows him to wherever he chooses to abide.
Michel in Mermaid Melody Pichi Pichi Pitch wants to turn the world into a rather odd-looking Mordor: rocks jutting above the clouds, giant neon DNA strands shooting out of the sky, and wings on every animal. Seeing his hideout, which already looks like this, disgusts Lucia and makes her wonder what would possess anyone to like that. Of course, it all has symbolic ties to his own origin.
As a subversion, the whole world at first appears like Mordor in Tengen Toppa Gurren Lagann and becomes more and more hospitable as the heroes approach the Big Bad's fortress. It's also why Kamina City is erected near the ruins of Teppelin.
Subverted in Princess Mononoke; Iron Town looks a bit like Mordor, with its destruction of the countryside and smoke rising from the furnaces, but instead of plain evil, Ashitaka finds a combination of good and ordinary human fraility. And in the end, the Forest Spirit lays waste to the forest in a flood of death and destruction while searching for his missing head.
After that, Iron town's iron shield becomes covered with vegetation when Lady Eboshi swears to do better.
The Smurf Village in The Smurfs was originally located in what was called The Cursed Land in the Johan and Peewit comic book story "The Flute With Six Holes" (later renamed "The Smurfs And The Magic Flute"). It would later appear in a flourishing animal-filled forest that would over time become a Sugar Bowl when the Smurfs got their own comic book series.
Outworld is depicted much like this in the Mortal Kombat movie. As Kitana tells us, it was once a beautiful land before its best warriors lost ten Mortal Kombats and the realm was taken over by Shao Kahn. She tells Liu Kang that the same thing will happen to his world if he fails to win this Mortal Kombat. Johnny Cage has perhaps the best line about what this land is like:
Johnny Cage: Liu, I hate this place. I'm telling you, I hate it. I'm in a hostile environment, I'm completely unprepared, and I'm surrounded by people who probably want to kick my ass. It's like being back in high school!
In The Lion King the Pridelands become a Mordor of sorts after Scar and the hyenas take over. The sky turns grey, all the plants die and all the animals are gone. As expected, when Simba defeats Scar and takes his rightful place as king, the land recovers perfectly (and apparently fast enough that the Pride doesn't starve in the meantime).note Simba's mother did advise Scar to temporarily leave the Pridelands during this period, and follow the herds. Scar refused out of pride, not wanting to want to leave the kingdom he'd spent years coveting.
The Lone Wolf series give us a few, including the Darklands, home of the Darklords, Ixia, home of the (not to be confused) Deathlord, and the Doomlands of Naaros. The Darklords' campaign was in part a terraforming project to make the rest of Magnamund more Mordor-like because they actually can't survive anywhere else without life-support equipment. It becomes a plot point near the end of the Magnakai series when the Darklords create a device that negates that weakness.
Notably, after the destruction of the Darklords, the good guys begin efforts to turn the Darklands into fertile wilderness again. After a few years of work, they realize that the process will take centuries of effort. After a decade, we only see a tiny corner of the Darklands green on the map.
The trope's title comes from the Dark Land of Mordor from Tolkien's The Lord of the Rings. Mordor combined both the "radiated evil" version of this trope (already seen in Mirkwood) and the "don't abuse resources" version (already seen in Isengard). However, the desert wasteland really makes up only the northwestern part of Mordor: Ironically, Sam and Frodo never find out the whole southern half of Mordor has a lake and great amounts of farmland to keep itself running, kept fertile by ash from the evil volcano; Sauron has to feed all those Orcs somehow.
The Silmarillion's Angband (the abode of Sauron's boss) combines the best of both hells. You've got arctic surroundings, barren desert plains, rivers of lava, giant slag volcanoes, vast underground dungeons, the works. Cold-Blooded Torture is the national pastime. Plus proximity to the Grinding Ice, the Land of the Shadow of Horror, the Gasping Dust, the Hill of the Slain, the Mountains of Horror, the Forest Under Night, and the Valley of Dreadful Death, all of which are also evil or horrible places. Just how Morgoth fed these orcs is not explored.
Said Valley of Dreadful Death is Mordor Up to Eleven, a place so horrifying that even the orcs of Angband avoid it. All we know is that the water there will kill you or give you horrific nightmares, and it's inhabited by the giant spider descendants of Eldritch Abomination Ungoliant (Shelob came from there). Beren, who had survived a litany of trauma and horror (including sneaking through Angband), could never bear to speak of what he experienced in this valley. Most of the other people who went in didn't come out.
William Hope Hodgson's The Night Land has the whole Earth like this after the death of the Sun and, it is implied, either some experiments gone horribly wrong or visitations from the Eldritch Abomination dimensions, or both. (Well, apart from a couple of huge pyramid cities where the last humans cling to existence.)
The Dragonlands in Shadowslayers, thanks to magic woven by Derrezen, the fellow who put the "Dragon" into "Dragonlands."
The Yeerk homeworld is portrayed this way in Animorphs. Also, in a way, the Yeerk pool.
Zaphod Beeblebrox: This place is the dismalest. Looks like a bomb's hit it, you know. Gargravarr: Several have; it's a very unpopular place.
Robert Jordan's The Wheel of Time series features the Blight, a festering wasteland where any bit of plant life is malevolent and the animals are even more so.
The Three-fold Land, also known as the Aiel waste, is very much a Mordor, with just about everything trying to kill you, and very little water.
By the end of the series, the Dark One is extending his reach beyond the Blight. Strange, bad things are occurring by the beginning of the fourth book; with the twelfth, the sky is blanketed with stormclouds that never break, and the plants are withering from lack of sun and rain, and the bad things are happening constantly across the entire continent.
The climax of Dan Abnett's Warhammer 40,000: Gaunt's Ghosts novel First & Only takes place in a necropolis. Gaunt and his team must forge through an underground maze that suck power from their equipment, including their lights, to a constructor for Men Of Iron, aka robots. Not only did a robotic revolt overthrow humanity's finest civilization, these particular ones have been seeped in Chaos. When Gaunt goes to blow it up, the Chaotic tainted Men come to life to stop them — horrifically malformed.
In Traitor General, the Chaos forces are actively working to make Gereon a Mordor: they are using machines that drain water to other planets, and planting crops that will grow wildly and destroy the land. In The Armour of Contempt, when they return, the process is considerably more advanced, with dead plants everywhere.
In William King's Warhammer 40,000 novel Space Wolf, when a group of Space Marines are searching for a missing group, they find a tunnel, leading to a dark and enormous cavern, filled with twisted animals and once-human nightgangers, culminating in an evil temple.
The whole damn world turns into Mordor in the third book of the Mistborn trilogy, with ash covering the entire planet to waist level, blotting out the sun and killing all plant life. But it got better.
That would imply it wasn't all Mordor already — the entire planet starts the trilogy post-apocalyptic and ruled by an Evil Overlord who's actually a Well-Intentioned Extremist, but that's small comfort to those living under him. It just goes downhill from there.
There's actually a rather interesting reason for this: when Rashek used the Well of Ascension, he first tried to get rid of the mists that were blocking out sunlight and causing plants to die by moving the planet closer to the sun. This worked, but it drove the temperature up too high for people to survive, so he created the volcanoes that constantly spew ash in order to block most of the heat.
Roland's world is basically Mordor in Stephen King's The Dark Tower series. Long before Roland was even born, a nuclear war destroyed the entire world, leaving only mutants and lucky survivors to rebuild the population. Thousands of years later, the Crimson King comes in and purposely destroys massive areas, poisoning them with radiation on purpose just so Roland can't follow.
In The Belgariad, the Big Bad Torak had his worshipers (literally, Torak's a god) construct a huge city. At the end of the construction, he had them create a giant tower of iron, which Torak used his divine powers to make * not* rust before it got put up. To cap it off, Torak made a giant black cloud and parked it over his city; it blotted out the sun for many miles around; after thousands of years, the countryside surrounding the city full of dead trees being consumed by fungus; water stagnated with no sun to evaporate it, and Torak's iron tower (after he knocked it over in a fit of rage) rusted down to a kind of semisolid goop. The place was definitely fragrant.
Zemoch from the same author's The Elenium is also like this; the fact that the Elder God Azash (particularly nasty even by Eldritch Abomination standards) has been imprisoned in the middle of it for milennia can't have helped.
It is theorized in The Malloreon that Torak didn't make the giant black cloud when they notice that the homeland of the new Child of Dark suffers from the same malady (although less advanced, that cloud having only been up for a couple of years).
In Heralds of Valdemar, the kingdom of Hardorn becomes Mordor after Ancar messes it all up with blood magic.
It is, indeed, a fearful place. The torrent, swollen by the melting snow, plunges into a tremendous abyss, from which the spray rolls up like the smoke from a burning house. The shaft into which the river hurls itself is an immense chasm, lined by glistening coal-black rock, and narrowing into a creaming, boiling pit of incalculable depth, which brims over and shoots the stream onward over its jagged lip. The long sweep of green water roaring forever down, and the thick flickering curtain of spray hissing forever upward, turn a man giddy with their constant whirl and clamour. We stood near the edge peering down at the gleam of the breaking water far below us against the black rocks, and listening to the half-human shout which came booming up with the spray out of the abyss.
Camp Green Lake from Holes. Flashbacks to the town's past show that it was a pristine lakefront Texas town, until Kissin' Kate Barlow cursed the place. From then until the present, it's a desert hellhole.
In The Last Unicorn it's stated outright that the area became a Mordor after King Haggard had his castle built there. Once the king is tossed into the sea by its crumbling, the land begins its climb back into a veritable Ghibli Hills. But it's going to be a slow process, King Lir has to return to help it along the path.
The Black Company in the first book of the series this trope is averted with the Lady's tower at Charm. In fact it is actually discussed by the protagonist that while it would seem dramatically appropriate for the land around the tower to be like this it also doesn't make a lot of sense. Who would want to live in a volcanic wasteland anyways?
Tales of the Sundered Lands: There is a "place," which as no name, which is blackened, burned out, covered with smoke and the home of evil spirits called Furies which can possess the unwary.
The Shadow homeworld Z'ha'dum in Babylon 5 resembles a science-fiction Mordor-analog, complete with a Great Eye that is ever watchful.note Though in name and pronunciation is sounds suspiciously reminiscent of Khazad-dum.
In Dead Ringers a run-down house was memorably described as looking like "a cross between Afghanistan and Mordor".
Netu in Stargate SG-1 is a good example of a science fiction Mordor. Sokar, a Goa'uld who takes the identity of the devil himself bombarded it to resemble hell.
In Magic: The Gathering, the Tempest cycle has Rath, wherein Mordor becomes an entire plane of existence where a perpetual storm rages in the sky.
Another recent example from Magic is the plane of Shadowmoor, which was once the idyllic sunny world of Lorwyn. After undergoing the cyclic process of the Aurora, the Ghibli Hills-esque Lorwyn becomes Shadowmoor, a world of perpetual night, filled with sickly vegetation and corrupted life.
And a third example comes from Shards of Alara: the plane of Grixis, a world completely devoid of white and green magic, ruled by demons and hordes of the undead.
Exalted has the shadowlands, which are an example of "Make Your Own Mordor": any massive act of slaughter over a large enough area will effectively open a door to the Underworld, something the Deathlords are quick to capitalize on. Zombies are created more easily in a shadowland, ghosts wander when night falls, and the flow of Essence is impeded.
Legend of the Five Rings has the Shadowlands. Thoroughly tainted by dark spirits and the touch of the Dark God, the place rots and corrupts everything within. The overwhelming presence of dark spirits makes magic much more difficult and dangerous to cast, and it teems with mutants and horrible creatures, many of which are outright immune to anything short of jade (which is pure and thus dangerous to them) or magic. Carrying jade protects the bearer from the taint, but jade is rare and valuable, and the strain of providing protection causes it to slowly rot.
The Mournland in Eberron, which was once the kingdom of Cyre before the dark magical cataclysm known as the Day of Mourning that ended the Last War, is actually even less convivial to Mordor; Mordor itself actually had living things (blighted, twisted ones, but still living). In the Mournland, healing doesn't work, the ground is littered with corpses, and there are even undead warforged.
Also, the Demon Wastes, who are closer to the "classic" Mordor (ie: Volcanic, ash covered land blasted by evil). Humanoids native to the area tend to have various signs of demonic corruptions.
In another D&D setting, Points Of Light, the Shadowfell could be considered an entire plane of this. It's a bleak, grey land where Undead are not only far more common but also far more powerful and the entire plane has a metaphysical aura that slowly crushes your will to live.
Deadlands: The Deadlands themselves. The twist is that any place can become like that if the inhabitants are driven into despair and fear. In the original Deadlands: The Weird West, there's only one major Deadland, in war-devastated Kentucky, and one area close to becoming a Deadland, the City of Lost Angels. But in the sequel, Deadlands: Hell on Earth, most of the former USA is kinda like that, and the Eastern Seaboard is one big Mordor.
Warhammer 40,000: The planet Krieg. It was once a habitable planet until its ruler declared independence from the Imperium. Five hundred years of atomic bombing later, Krieg became a futuristic Mordor.
The setting as a whole is neck deep in blasted dead worlds, Daemon realms, ash wastelands, Necron-scoured desert rocks, volcanic hellscapes and generally every other unpleasant place to live imaginable. In general, if you were to take an A3-sized map of the galaxy, then stick a pin in a place it's a bad idea to visit, you wouldn't be able to see it.
The land of Chaos Dwarfs in Warhammer - known generally as the Dark Lands - manages to be both Mordor and a Polluted Wasteland at once. It started as a dark volcanic wasteland... and then the Chaos Dwarfs brought in thousands of slaves to start strip mining and heavy industry. It's a wonder how they manage to feed their single giant city in such conditions.
There is also the (much smaller) Desolation of Nagash on the shores of the Sour Sea at the foot of the citadel of Nagashizzar - which is a less industrial, more undead version. Though it does pretty much border the Dark Lands.
The Northern Wastes or Umbra Chaotica surrounding the northern polar rift into the Realm of Chaos would also count - its particular flavour of nastiness being found in merciless barbarian tribes, waves of wild magic and horrific mutant monsters spawned from the meeting of the first two.
The realm of Karzahni in BIONICLE definitely fits. The ground screams with every step you take, waterfalls flow with dust, volcanoes erupt with burning ice, and any lazy Matoran would be turned to stone. When the ruler left, the Toa Nuva liberated the mentally and physically broken Matoran and Toa Gali proceeded to destroy the place in a massive flood.
Age of Wonders: The undead factions often have blackened wastelands around their cities (especially the last campaign level), complete with dead trees, active volcanoes, smoking fissures and skeletons abound.
Battalion Wars: The nation of Xylvania is a complete wasteland with green acid pits everywhere and dead trees amuck. The sequel's past missions in Old Xylvania looked similar except it had the Iron Tower which looked just like the tower in Mordor
The Elder Scrolls III: Morrowind: Red Mountain, a volcano inhabited by the game's Big Bad and perpetually shrouded in "ash-blight". The Powers That Be in the game world have gone so far as to erect a magical fence around the mountain to keep the monsters trapped therein, with limited effectiveness.
And, in extension, Molag Amur and the Ashlands, which are essentially the lava flows from Red Mountain. In fact, much of the island is barely inhabitable due to being mostly either arid or rocky. The animal and plant life that does survive seems to have evolved quite differently from the rest of Tamriel.
Mehrunes Dagon's planes of Oblivion from The Elder Scrolls IV: Oblivion is a Mordor with lots of fire. The gates to Mehrunes' Oblivion in the "real world" radiate scorched land and ominous clouds. The other planes of Oblivion are ruled by other entities have appearances reflecting their personalities and powers, and as such have different appearances. Or at least in theory. Sheogorath's realm, the Shivering Isles, is split into Mania and Dementia. The latter area is a mild slice of Mordor somewhat darker than Morrowind's swamps, but some locations there are more like the Heart of Mordor.
The original game (Kalimdor and the Eastern Kingdoms; with the Cataclysm expansion, some of these zones have actually begun to heal back into normalcy, while others have gotten even worse): Searing Gorge and Burning Steppes, full of volcanic cracks in the ground and high-level nasties. The Western and Eastern Plaguelands, thoroughly corrupted by the Scourge's plague of undeath. Felwood, a demonically corrupted and really unhealthy-looking forest. The Blasted Lands, a blasted, lifeless desert with a perpetually black, stormy sky. Silithus, full of giant bug hives.
The Burning Crusade (Outland): Outland in general is a magically devastated world crawling with demons and full of inhospitable locations. Some areas make an exception to this; the ones that most definitely do not include the following: Hellfire Peninsula, a barren, broken wasteland with a highway of bones going across it. Shadowmoon Valley, another dark wasteland with added volcanic activity. The Netherstorm, an area consisting of nothing but islands of land floating above the Twisting Nether. The Bone Wastes, literally an enormous bomb crater littered with bones tossed from their previous resting place inside a now-exploded necropolis.
Wrath of the Lich King (Northrend): Icecrown is Mordor down to a T; complete with big black gates guarded by fearsome, disfigured creatures, an evil, necromantic lord bent on destroying the world as we know it and even a large magical eye atop a tower. Only difference is it's covered in snow instead of ash. Intentional on Blizzard's part: the entire area is separated by huge ramparts with Gates to block passage. The one directly in front of the Citadel (which already looks like Barad-dûr) is called "Mord'rethar." One does not simply walk into Icecrown. A flying mount is needed to get around the place.
Cataclysm: The Firelands and its accompanying daily quest hub, the Molten Front. Players fight against the forces of Ragnaros here. The landscape is like the Burning Steppes or Hellfire taken Up to Eleven, full of fields of lava pools, and areas that are constantly burning. The only green area is the Guardian of Hyjals' base, Malfurion's Breach, where they have grown the Sentinel Tree.
Dragon Age has an underground Mordor, ominously named The Deep Roads. Forget the black-ash-ridden skies! This place has no skies at all, just an unconscionable number of tunnels, originally built by Dwarves (whose architectural sensibilities just have to raise some questions) and subsequently conquered by the Darkspawn hordes. Forget the desolate, depressing winds or murderous cold! This place has lava rivers, and the air is hardly breathable at best, and filled with the blood-taint that will make you die or turn into Darkspawn at worst. The Dark Lord? A mad, tainted Dragon-God that seeks to corrupt the whole world. And then there are his sleeping brothers.
Additionally, surface lands that are overrun by Darkspawn become barren and corrupted (or "tainted" as characters in the game call it), and the animals that inhabit those land become twisted, bloodthirsty mutants. It is possible for the lands to recover once the Darkspawn and tainted are killed or driven out, but it's a very long process.
The Anderfels has been ravaged by three of the Blights which have started in the area, leaving most of the landscape scarred and barren as a result, with roving bands of Darkspawn commonly seen above ground even between Blights. It's not surprising that the Grey Wardens hold a lot of power and prestige in the Anderfels and maintain their headquarters there, located at Weisshaupt Fortress.
EverQuest and EverQuest II both have two realms of volcanic mountains; Lavastorm and the Skyfire Mountains. In EQ1, the Muramites are doing their best to turn the entire continent of Taelosia into Mordor. Perhaps surprisingly, the Muramites home realm isn't too harsh for the most part, although being an upper level area it suffers from a severe case of Everything Trying to Kill You.
EQ1 has the Plane of Disease, a bloated, disease-ridden, spider and fly infested place with ingrown hairs in the place of trees and a river of bile running through it. This, incidentally, is the nice part of the realm, as next up on the platter is the Ruins of Lxavanom... also known as the intestinal crypt of doom.
Then there's Volska's Husk, a place of golems, imps, lava, cult members... all living together in the hollowed out husk of a titanic lava snake. Don't forget your asbestos robes!
The Dark World of The Legend of Zelda: A Link to the Past was really the Sacred Realm of the Gods after Ganon got through with it. Zelda does this a lot, but the original Dark World is the most prominent example.
The Twilight Realm in The Legend of Zelda: Twilight Princess is perpetually covered in bleak light and dark clouds. Besides that and the creepy architecture, though, it's actually a pretty nice place.
The Death Faith's lands in the Sierra game Lords Of Magic is basically the marshlands of evilness, dominated by an ominous, towering cliff with a skull carved into it... Oh, and the people who live in the land are all since childhood trained murderers and, as such, the life expectancy within the land's borders isn't especially long, as a merchant in the Death capital's marketplace helpfully reinforces: "Be sure to take advantage of our lifetime guarantee. It's good up to thirty days..."
Bowser's Castle in the Super Mario Bros. games almost always exists in Mordor. It rarely has a set name, though Dark Land/World and Valley of Bowser are some that have been used. Such lands are filled with barren rocks, volcanoes, rivers and lakes of lava, and if it's lucky enough to have vegetation, fetid swampland. Especially noteworthy in Super Mario Bros 3, where part of Dark World was so dark that you could only see your current location on the map screen, not the whole map.
Guild Wars begins with the characters' kingdom becoming Mordor when the Charr (the game's stand-in for orcs) unleash a massive sorcerous assault of flame and crystalline meteors, rendering the entire kingdom into a broken desert, featuring rivers of tar and a blood-red sky. The first campaign takes place in a series of Mordors. First your kingdom is razed to ash, then after a brief interlude in the series of hells with an excursion to the Ice Caves and a brief pass through the lush jungle crawling with with The Undead and Knight Templars, you're thrown into a scorching endless desert hell. Then you go to a more standard hell-esque Mordor that makes even Sauron's Mordor look like a pleasant vacation spot. Oddly, the Charr homelands in the Eye of the North expansion is actually a pretty pleasant place.
Guild Wars: Nightfall: The Realm of Torment, which is the home of the fallen god Abaddon. Caves made of flesh? Check. Teeth sticking out of the ground? Check. It's even got some fetid swampland of its own. And every part of it has its own delightful status effect to offer.
Mhaldor in Achaea is Mordor on an island. The streets are littered with corpses, piranha fish swim in every pond and even the plants are carnivorous — that is, the ones that aren't withered by the toxic red mist. The city patrons are Apollyon and Shaitan, also known as the Twin Gods of Oppression and Suffering. It's a nice place for a picnic.
Taros, from Total Annihilation: Kingdoms, is a textbook Mordor clone. Like most Tolkien ripoffs it lacks any ecological explanation for how the barren volcanic steppes can support a population, unlike the original.
By the time it gets like that it has no human population, it's all undead and demons.
The various worlds named Filgaia in the Wild ARMs series are virtually always like this, but usually long after the event that caused it. Sometimes this was caused by a Fisher King scenario (another of which might also be arriving in the same story), but the original cause has long since departed, leaving the planet's ecosystem to try to slowly clean up after itself. Compare Tatooine from Star Wars.
Final Fantasy VI, you actually get to watch the planet be taken over by an Ax-CrazyMad God, and the landscape goes from lush green meadows and blue seas to sickly grey and brown wasteland and murky purple-ish seas.
Dissidia 012 Final Fantasy, the north-west continent dominated by Onrac. The skies are red, there's streams of lava, stretches of desert, and the lair of the Big Bad is on a floating volcano island off the coast.
The planet Fargett in Star Ocean: First Departure is a desolate wasteland, in contrast to the lush, Earth-like environment of Roak, the home planet of the game's main character, Roddick Farrence. The planet Fargett is run by an Evil Overlord named Jie Revorse, who essentially turned the planet into The Empire.
In Runescape, the Wilderness is a dangerous volcanic wasteland populated with skeletons and other nasty things. It is also one of the only places where other players can attack you and get all your stuff if they kill you. Originally, it looked a lot like the "normal" parts of the world, but fighting during the God Wars desolated it.
Char from Starcraft is your standard Planet Mordor, all lava and volcanoes and blasted dead black plains.
Rather accurately described with: "Char. If Hell ever existed - this is it. Oceans of fire, tectonic storms and an atmosphere that'll burn a man alive."
Barathrum is a subversion, actually. It's a world in the process of being born, hence the higher than average metal content of the surface. The overall effect is about the same, though.
Eversion's world turns more and more into this as you progress through the game. The environment takes on a definite Mordor feel with the sixth "everted" world: the vegetation is covered in thorns (which are Spikes Of Doom for all intents and purposes), the Goomba-like enemies start to show their teeth, everything turns into a spray of Ludicrous Gibs when killed, the music sounds horribly distorted, and demon hands pop out.
But that doesn't end there. Wait until you get to X-8. Enemies cannot die there (and respawn if you kill then in a different layer), the music is very creepy and is not even chiptune at all, and black takes up most of the pallete.
American McGee's Alice pulls this off: as soon as you defeat the Big Bad, the entire world loses its sickly nightmarish quality and reverts to a much nicer place, complete with blooming flowers and chirping birds. Justified by the fact that it's all happening in Alice's head.
Legacy of Kain has two examples. One is Dark Eden, the lands surrounding a tower which spews forth an ever-expanding dome of magic. The dome is the result of three Pillar Guardians pooling their powers and it warps everything it touches. The inside of the dome is standard fare with roiling lakes of lava and warped mutants with poisonous blood. The second example is Nosgoth itself, as it turns out that Kain's decision at the Pillars was fixed to result in destruction either way. As it is, Kain chose to live and rule, which causes the world's balance to waver, resulting in the worldas it is seen in Soul Reaver.
The Rogue Isles is known as the City of Villains for a reason. Places that aren't a Vice City or Supervillain Lair are a dilipidated mess of decripit slums, or ruined and abandoned buildings. The first zone players enter, Mercy Island, fits this trope to a tee.
Its Spiritual Successor Headshoots is founded on an ash plain filled with undead creatures and burnt trees, and Headshoots' direct sequel Syrupleaf is set on an arctic glacier with no vegetation to speak of and haunted by hideous demons. Those dwarves sure know prime real estate.
As of the 2012 update, Evil biomes are this trope more than ever. Nothing says Fun like raining goo that makes dwarves haemorrhage from their lungs, bodies and body parts spontaneously rising up as undead, or if you're really unlucky, cursed fog banks that instantly turn living things into nigh-unkillable, highly aggressive husks.
Planets colonized by the Zuul in Sword of the Stars start taking on a very Mordor-ish bent.
In Fable, the landscape that is near places of great evil, such as Darkwood or Wraithmarsh, are very creepy and ruined.
Crocodile Island from Donkey Kong Country 2 is oddly both Mordor and a Polluted Wasteland. It's both a Death World filled with dangerous monsters and polluted to the point it makes any real life environmental trainwrecks look quite pleasant in comparision. It actually sinks into the ocean after the final boss is defeated.
The area around the Sea of Black Tears in Brütal Legend is designed after Death Metal album covers. All graveyards, twisted and ruined churches, dead trees, and candelabras everywhere.
Malachor V in Knights of the Old Republic II. An entire Mordor planet echoing with the deaths of millions of people who were slaughtered there. High-ranking Sith would bring captured Jedi there because it would break their wills and make them easy to convert to the Dark Side.
In Spore, planets in the Space Stage with a terrascore of 0 are either hot, with lava and random volcanoes, or cold, with frozen seas and storm clouds. A more fitting example would be the cyborgGrox's planets, which the Grox convert into barren wastelands because that's the only environment they can live in.
In Sacrifice, Charnel's realm of Stygia is a dark and gloomy land inhabited by Charnels minions.
Played with in El Shaddai: Ascension of the Metatron. The fallen angels known as the Grigori are "perverting mankind's natural evolution" from their Evil Tower of Ominousness, hidden in another dimension. When you arrive at the exterior, the Tower, and the city surrounding it certainly looks twisted enough, with it's blood red hues and lightless sky. Yet as the music plays, and the fireworks erupt through the air, you realize: The people corrupted by the Grigori's gifts of forced advancement are celebrating.
To a slightly lesser extent, there's the Sierra Madre from Dead Money, which is polluted by a lethal and corrosive red smog created by the aforementioned Big MT facility, and inhabited by Ghost People, hazmat workers who were trapped in their suits by the corrosive gas and mutated into zombie-like creatures.
Likewise Fallout 3 has an expansion pack area titled The Pitt, the pollution-clouded and irradiated ruins of Pittsburgh, where most humans have degenerated into Wildmen, or worse, the skinless ape-like beasts known as Trogs, and the few "normal" humans here (other than Ashur and his wife and infant daughter) are either disfigured and sterile Slaves or Pitt Raiders.
Before those, there was the Glow in Fallout 1, where Rad-X is required to survive any significant length of time.
Hyperdimension Neptunia mk2 has the Gamindustri Graveyard, the resting place of those who worshiped the evil goddess Arfoire and the home base of the Arfoire Syndicate of International Crime. It also has an ominous tower that looks like Barad-dûr.
Destin Island from Sky Odyssey might not have evil creatures, but it looks just like the trope image. The mountains here are ash black, cragy, and complete with an active volcano. Other parts of the island look almost as bad with little to no plant life and hurricane like thunderstorms being the most common type of weather. In a subversion however the Tower of Maximus and Garden of Eden hidden near the center of the island are absolutely gorgeous.
The last world in Something. It's a barren field with a Ghost House filled with ? Mushrooms, an obstacle-filled Fortress, and Ballser's Castle. Ballser is menacingly orbiting around his castle, waiting for Mario to enter.
Mass Effect: the vorcha homeworld Heshtok has been described as "hell, plus vorcha". It's such an unpleasant place that the vorcha, despite their 20-year lifespan, have actually evolved into a "perfect race" since they can adapt to survive nearly anything short of headshots. In addition, any world that bears the touch of the Reapers will typically have blasted and ruined cities, massive casualties, and in most cases fires that are visible from orbit, although outside major population centres the damage tends to be less extensive.
Succession runs of Dwarf Fortress are frequently played out in such a way that the settlement either is or becomes a blight on the face of the planet. Take this quote from the renowned Boatmurdered playthrough:
At this point, we have somehow managed to create THE root of evil in the dwarven universe. Here is what it must look like from the mountainhomes: 1) Dwarves go to Boatmurdered and disappear. 2) Lava comes out of Boatmurdered and destroys the surrounding environment no less than three times a year. 3) A maniacal dwarven supervillian comes out of Boatmurdered and goes on a killing spree. Shit, there are probably entire fucking sagas that are being sung about the evil fortress of damnation known as Boatmurdered.
More often than not, the settlements are founded in places that are already prime Mordor material, to make things more !!Fun!!. Such places are typically almost inhospitable, infested with undead, or both. Usually both.
Drekmoor in Disney's Gummi Bears. Homeland of ogres, ruled by Duke Igthorne, and a perpetually nasty place— everything there is either poisonous, carnivorous, explosive, or otherwise dangerous. Even the rabbits are meat eaters.
Subverted in the tie-in comics which show what happened directly after the Season 2 finale. The Changelings actually landed in a Sugar Bowl that resembles the G3 version of My Little Pony, only inhabited by cute cat-like people. And then they turn said Sugar Bowl into their own personal Mordor.
Arguably, another (Tartarus itself, no less) is referenced in one of the previous episodes.
The battlefields of the First World War are the very image of Mordor. Blasted hellscapes of twisted trees where nothing lived and men drowned in the mud. The "no-man's land" between the two front line trenches, which looked more like the surface of the moon than the Earth. The battlefields were most likely Tolkien's inspiration for Mordor, as he served in the war as a young officer.
They also helped him concieve the Dead Marshes, a haunted swamp.
This description of Stalingrad during the battle there certainly fits the image:
“The street is no longer measured by meters but by corpses…Stalingrad is no longer a town. By day it is an enormous cloud of burning, blinding smoke; it is a vast furnace lit by the reflection of the flames. And when night arrives, one of those scorching, howling, bleeding nights, the dogs plunge into the Volga and swim desperately to gain the other bank. The nights of Stalingrad are a terror for them. Animals flee this hell; the hardest stones cannot bear it for long; only men endure.”
Industrial deserts. In countries where environmental laws or pollution reduction technologies are lax or nonexistent, the pollution emissions of the factories and plants may poison the environment for good, killing all plants, trees and animals within radius of tens of kilometres. This so-called "industrial desert" or "industrial wasteland" - usually accompanied by smog - can resemble Mordor a lot. The Ruhr Valley in Germany used to be an Ur Example of this.
When an Apple employee visits the city-sized FoxConn factory where iPods are made, he is said to have been "sent to Mordor."
The Bonneville Salt Flats of Utah. The whole area is basically a plain of salt. There is a highway with a couple of gasoline stations, an 87-foot-high statue of a tree made by a Mad Artist, and that's about it. No plants, no animals, and the whole thing is surrounded by some barren-looking mountains (though these do actually have a working ecosystem).
Ethiopia's Danakil Depression is an, um, interesting place with 130-degree temperatures, sulphuric acid volcanoes and lava lakes. Google 'Erta Ale' some time and you'll see exactly what we mean; one part of it is actually called the "gateway to hell" by locals.
Death Valley, despite its name, is NOT an example. You still don't want to go there without water, though.
250 million years ago, a huge, continuing volcanic eruption in what is now Siberia (which today is more like The Lost Woods) reduced pretty much the entire planet to this. Fortunately, this didn't last.
A colossal meteor impact had done the same during the Cretaceous-Tertiary boundary 65 million years ago, though there are those who beg to differ.
The Dasht-e Lut, the largest desert basin in Iran and confirmed by NASA to be the hottest place on Earth, with a recorded maximum of 71 degrees Celsius (159 degrees Fahrenheit). Most notably the area called Gandom Beriyan, an area of hardend black volcanic lava whose temperature differential with the surrounding terrain causes constant winds. No life is said to exist here.
Washington, D.C. is often referred to witihn the blogosphere as "Mordor on the Potomac".
It's actually quite green and lush, and very elegantly laid out in a wheel - but it was originally a malaria-infested swamp and was a pretty unhealthy place to live until malaria was eradicated in the US.
On that thread, Jamestown was not a particularly great place to start a settlement. The island the settlement was on had actually been abandoned by the Native Americans in the area because they considered it too poor and remote for agriculture. It was isolated, swampy, was small, plagued by mosquitoes (and malaria), and the water was brackish and unsuitable for drinking. On top of that, settlers arrived too far into the planting season to really get anything going and many of them were not accustomed to doing hard labor. As a result, 51 settlers died in the first few months of settlement, and in the winter of 1609-1610 (known as "Starving Time"), only 61 of the 600 settlers survived.
Southeastern Idaho. It's flat, treeless, and dry. In the winter, the temperature can drop to 30 degrees below zero. Natural characteristics aside, it's Idaho. That in and of itself makes it Mordor.
All the wimpy Earth "Mordors" couldn't hold a candle to Venus. The sun is hidden beneath toxic clouds, which is a mercy, as due to a runaway greenhouse effect it's already the hottest planet in the solar system, even though Mercury is closer to the sun. Atmospheric pressure is so high -as much as about 92 times that of the Earth at sea level, or about 1km under water- it would crush like an egg anyone not properly equipped. The clouds emit lightning and acid rain- not our wimpy, slightly-lower-pH acid rain, but battery acid rain. (It evaporates 25 km above the surface, but still...) And all of this is partially thanks to its many erupting volcanoes. And just to make it a little creepier, it spins the wrong way. Yes, it spins clockwise, unlike all of the other planets in the solar system. It seems more like the homeworld of the ultimate evil in a fantasy novel than the planet next door.
And that was Venus. Nothing but nothing—except it scared me. It was like circling a haunted house in deep space. I was scared gutless until we got out of there. I think if our rockets hadn't gone off, I would've cut my throat on the way down. It's not like the moon. The moon is desolate but somehow antiseptic. That world we saw is utterly unlike anything anyone has ever seen. Maybe it's a good thing that cloud cover is there. It was like a skull that's been picked clean—that's the closest I can get.
Jupiter's moon Io has to be close. The most volcanically active body in the Solar System, tidal forces from Jupiter and the other major moons ensure that it is in a state of almost constant eruption, covering the surface in lava flows and sulphur compounds. It's also tidally locked to Jupiter which means that for half of the moon you can't escape its mass hanging in the sky. And for extra fun the entire surface is bathed in radiation from Jupiter's magnetosphere and is connected to Jupiter by the Io Flux Tube which causes lightning strikes between the two. In the novel 2010 by Arthur C. Clarke, Heywood Floyd compares Io to Mordor.
Bouvet Island is the most isolated piece of land on earth—1000 miles north of Antarctica and 1500 miles from South Africa. It's also buffeted by frigid hurricane-force winds, its landscape consists of snow and crags...and it stinks of penguin and seal feces. Smack in the middle of the South Atlantic with only chartered boat transport available, it's sort of a holy grail for adventure tourists who want to go everywhere...but that's about the only reason to go there.
Lanzarote (one of the Canary Islands) is Mordor, in some way. Most of its surface is covered with black ash and rock, and almost the half of the place is completely deserted form any plant. There are no dark clouds, thought, but this is even worse: the average quantity of rain per year is lower than in some parts of Sahara. These◊ are◊ some◊ examples◊. It also has some cool beaches, too.
The southern half of Montserrat, a British territory in the Lesser Antilles, became this trope when its Soufriere Hills volcano awakened in 1995. Its capital city of Plymouth and communities throughout two of its three parishes were left abandoned and buried in ashen mud, and subsequent volcanic unrest has barred all plans for re-colonizing the evacuated Exclusion Zone.
Much of the interior of the "big island" of Hawaii is a baking hot black volcanic desert, covered in the flow from Mount Kilauea (which has been erupting continuously since the mid-eighties). The ground is littered with sharp fragments of volcanic glass that will cut your feet if you walk in sandals, and boiling sulfurous jets of steam spout up unexpectedly. However, it's eerily beautiful and awe-inspiring in its bleakness, like the surface of another planet - especially if you're in a place where you can see molten lava rolling down the mountainside.
The Atacama Desert in South America, made up of salt basins, sand, and lava flows. It's accorded the dubious honour of being the driest desert in the world. Average annual rainfall is one millimetre, and some weather stations in it have never received rain. Mountain peaks over 22,500 feet (6850 metres) are completely devoid of glaciation. The Top Gear Bolivia Special asserted that it's so dry even bacteria can't live there. Although this is a significant exaggeration, it illustrates just how inhospitable the area is.
Centralia, Pennsylvania. A still-burning underground coal seam has rendered it a ghost town, fissures and sinkholes dotting the landscape, blanketing the town in Silent Hill-like smog and toxic gases such as carbon monoxide.
Iwo Jima, or in modern Japanese, Iōto. The name means "Sulfur island" in Japanese, and the terrain is indeed rich of sulfur, making it true Mordor. Not to say it was the venue of one of the most bloody island battles in World War II. Mount Doom optional, as there is ongoing volcanic activity omnipresent.