The trope is where a cemetery, temple, forest, etc. is considered holy... to the forces of evil. Whether it was the site of great and terrible crimes, incredible bloodshed, unholy rituals to malevolent beings or other atrocious acts, the very ground itself and any surrounding lands are now cursed. Exact results vary, but the most common are that evil is stronger, good is weaker and things buried here don't stay down for long.
If it's the burial place of some malevolent being, it will also be a Supernaturally Marked Grave. May otherwise be the result of a Leaking Can of Evil, an Unholy Nuke going off, or just because Evil Tainted the Place.
The site may be a Mook Maker for Night of the Living Mooks. If it produces way more zombies than it should, that is a Clown-Car Grave. If the effect covers an entire battlefield, that is a Corpse Land.
When this is a video game level, that's Big Boo's Haunt.
- The third Captain Underpants, the one with the long title about the lunch ladies, had a very good page image about the hill where they buried the lunch ladies being haunted.
- Stephen King's Pet Sematary, which did not produce overtly undead resurrectees, but there definitely was something wrong and horrible to those who rose from it.
- In Nick Perumov's Keeper of the Swords series, the entire world of Evial is like this, due to the presence of the entity known as the Western Darkness. Any graveyard can go bad, sooner or later, necessitating the presence of clerics and necromancers to deal with the undead. And necromancers are the safer, saner option: the sacrifices they need to stop the undead are just cats, while the priests will torture or burn some human sinners.
- There are two levels of this surrounding the mountain Shayol Ghul (the site where the Dark One's prison overlaps with the living world) in The Wheel of Time. Travel north from the Borderlands, and one will find not the cold subarctic wastes one might expect but, thanks to the Dark One's touch, the Great Blight, a diseased jungle inhabited by deadly and unnatural creatures. Travel beyond that and you come to the Blasted Lands, the direct environs of Shayol Ghul where the corruption is so strong that nothing can survive at all there. Both regions become increasingly eldritch as the series progresses and the Dark One's prison weakens, warping time and space in Shayol Ghul's environs.
- In the backstory of Angel Wolfram & Hart de-consecrated the grounds of the Los Angeles branch office with the spilling of a serial killer's blood in the foundation. The ghost of that killer continued to haunt the offices until Angel & Co brought him back to life, after which they locked him in a sarcophagus for the rest of his eternal life.
- Several Power Rangers series have tried to come up with better reasons than the original (in which it never came up) for why the villains only ever attack one city. For the demons in Power Rangers Lightspeed Rescue we get a doozy: The city of Mariner Bay is built upon their sacred ground. If they retake it and recreate their palace there, they'll become unstoppable. That means the city has to go.
- In Ars Magica, an area can take on an "infernal aura" if it is dedicated to satan or if something suitably atrocious happens there. In extreme cases, it warps the area into an Eldritch Location with multiple layers of reality, each more profoundly tainted than the last.
- In Deadlands there is a whole mechanic for this, called Fear Levels. Ground becomes unhallowed if local Manitou (demons) become strong, and Manitou feed of human fear. So scare the populace, and their fears become real.
- Dungeons & Dragons
- Unhallowed ground can be created with the spell unhallow. This strengthens undead against turning and provides bonuses against good creatures in general.
- The 1st Edition Dungeon Master's Guide mentions "Evil Areas", places where Evil has created a special power base that reduce the chance for clerics to turn (repel) undead. They can only be destroyed by purifying them in some way, such as pouring holy water or casting a Bless and/or Prayer spell.
- The Book of Vile Darkness supplement describes how evil actions can taint an area. The site of a murder or evil sacrifice might give people nightmares and make it more likely to evil undead to arise from corpses in the area. The site of an evil temple, massacre, or the abode of a fiend or powerful undead monster can be unnaturally cold and slightly warp objects left in it. A place of great evil that saw daily human sacrifices over centuries, or where someone built a portal to the Lower Planes, is tainted enough to traumatize creatures mentally and physically, and may impede the casting of spells like hallow or consecrate. And an unspeakably evil act like genocide or the birth of a malevolent god can leave a powerful dark aura that sickens and corrupts any creature that enters the area, and permanently warps the surrounding landscape and weather patterns.
- Exalted has the Shadowlands, areas where normal Creation and The Underworld overlap and the dead can walk freely. They're often created by vast death in an area or through some vile Necromancy.
- Pretty much everywhere in Ehdrigohr. Since the land is infected by the Shivers, who come out every night, every burial ground that has not been properly consecrated risks sparking a Zombie Apocalypse.
- In Vampire: The Masquerade and Demon: The Fallen, the fallen angel Kupala is bound within the soil of Eastern Europe.
- The entire continent of Wraeclast in Path of Exile is, according to the lore, an unhallowed ground where the dead refuse to stay down, handily explaining the hordes of undead roaming the levels.
- Warcraft III: Undead buildings spread a corruption called Blight, which turns ordinary ground into a black, fog-emitting morass with bones sticking out, and makes undead units regenerate health while on it. Undead buildings (save for the Necropolis) can only be built on blight, while non-undead buildings dispel it in a large radius when built. It can also be removed by area-of-effect dispel-magic spells, a good way to infuriate an Undead opponent since it prevents them from building until they put down some more blight. In The Frozen Throne expansion, the Undead can buy an item to create a circle of Blight at a location without needing to wait for a slooow-building Necropolis.
- World of Warcraft: The Death Knight class has a talent ability called "Desecrated Ground". It corrupts the ground beneath the user removing and making him/her immune to effects that cause loss of control of the character. Paladins have a more or less corresponding ability called "Consecration", though it's simply an Area of Effect spell that deals holy damage.
- Not literally unholy, but Zerg Creep in the StarCraft universe has a function analogous to Blight, though biological in nature. Unlike Blight, it slowly dies if there are no Zerg structures to maintain it but Terran and Protoss structures cannot be built on it. In Starcraft II, Zerg units get a speed bonus if moving on Creep, and it can be spread via Creep Tumors and stationary Overlords in addition to buildings.
- Silent Hill is a textbook example. The land where the town is built was considered a haunted place by the local Indians before the settlers came, and after the town was built eerie things occasionally happened. Then a whole lot of evil went on and as a result the dark force inhabiting the land became much more active. Now the town summons anyone with a Dark and Troubled Past and torments them with monsters and visions.
- The Shadow Temple from The Legend of Zelda: Ocarina of Time. Monsters like Redeads, Gibdos and Stalfos roam its halls and the temple itself is a gathering place for Hyrule's bloody history of greed and hatred.
- The village of Tristram in the Diablo series gradually became one of these after Diablo corrupted the town's cathedral. For twenty years afterwards rumor persisted of the land being cursed for any who tried to settle there.
- Dragon Age II has the entire city of Kirkwall. It's revealed the city's very architecture is designed to harness arcane power and was used in an immense blood ritual, the sacrificing of thousands of slaves secretly abducted from the slavery trade, which took place during the Tevinter Empire days. This mass slaughter may have been to fuel the very ritual Tevinter Magisters used to enter the Black City and unleash the Blight on Thedas. As a result the veil is noticeably much weaker in Kirkwall with demons, blood mages and abominations far more frequent that any other location. Worse still the Chantry and Templars decided that the old slave prison was the best place to house the Circle of Magi. Unsurprisingly the death rate for Harrowings, a trainee mage's final rite of passage, is far higher in Kirkwall than anywhere else.
- Star Wars: The Old Republic: The Dark Temple on Dromund Kaas, where the Emperor entombed some of his most deadly enemies, and where their power lies dormant, until an unwitting expedition opens the place and is driven mad, if not outright taken over, by the personalities of the entombed Sith.
- The Sith temples in Korriban the former homeworld of the Sith race. A few Jedi who entered the ruins are corrupted by the spirits of the fallen Sith lords.
- On Voss is a region known as the Nightmare Lands. Those who enter often never leave, and those that do are likely to be driven mad. The source of the corruption is a being called Sel-Makor, a creature of the Dark Side created when the Jedi began teaching the natives the ways of the Force, using it against the Sith. In the centuries that followed, Sel-Makor has spread its influence, inducing hatred and violence between the Voss and Gormak and growing ever stronger from the conflict.
- Devil Summoner: The city itself whenever parts of it gets distorted by the Alien Dimension thanks to Sid.
- It is implied that Carnate Island from The Suffering is an inherently cursed settlement - the various disasters and lapses in human decency being the island's attempt to get rid of the humans that settle there - and that the Malefactors (the monsters of the game) are the Island's last resort in doing so. The same could be the case for Baltimore.