12 Monkeys has the Red Forest, Another Dimension that exists outside of time and takes the default form of an endless forest of red leaves and grass, and containing a house that constantly cycles through building and deconstructing. Because its not governed by normal temporal rules, people who go there can communicate across time, re-live all their happiest moments at once, or even use it to travel back into their own past selves. The ultimate goal of the Army of the 12 Monkeys and the Witness is to cause a Time Crash that will collapse reality and send everyone who's ever lived there.
Ash vs. Evil Dead: The last episodes of the first season see Ash return to the cabin from the original film. It already has this vibe, due to the fact that the woods in the immediate area appear to have been rendered completely lifeless, but it definitely hits this in the season finale, due to the ritual Ruby performs in the basement — the cellar door bleeds when Kelly tries to force it open, an eye appears on the wall, a mouth (with functional tongue) appears on a doorknob, and innocent bystander Heather suffers a Cruel and Unusual Death as the cabin seems to specifically target her. Fortunately, Kelly setting the place on fire seems to kill it.
The House in Beyond the Walls is so incredibly vast it might be infinite. Under certain conditions, it definitely is. It even has its own forest that is locked in daytime and is implied to hide whole oceans in its bowels. It can also change its layout, depending on the actions of its inhabitants.
Candle Cove, the location of said Show Within a Show, is strongly implied to be one of these. Eddie's Realm is also one, being a nightmarish mockery of his family's home which he controls; whether or not it and Candle Cove are the same place is unclear.
The No-End House. It moves on its own, its first five rooms constantly change their contents to depict visitors' worst fears, and its last room is a neighborhood-sized Pocket Dimension inhabited by clones made from peoples' memories of their loved ones, which feed on their memories until they're left Empty Shells.
The "summer house" where the Peach family live. It's field without end, where it's always a summer day, the "plants" growing there are actually severed human body parts, and the house itself is always in the distance no matter how far you walk. The only way to reach it is to walk through one of the random doorways standing in the field (another one connects to the real world, while a third leads out into space). Also, the house appears moderately sized on the outside, but is massive on the inside. It also contains the home of the Pestilent God.
Crime Scene: The Vanishing at The Cecil Hotel: The docu-series explores the history of real-life Hell Hotel, The Cecil, and discusses the many online conspiracy theorists who believe the hotel itself is a "nexus of dark energy" and/or a gateway to hell. The series presents several historians who explain that the hotel is located on Los Angeles's Skid Row and most of the unsavory happenings there are explained by the mundane forces of poverty, mental illness, and drug addiction.
The Doctor has been to the extrauniversal E-Space, multiple parallel universes, and once simply PARKED OUTSIDE REALITY. Humanity found a way to build a space station that would continue to exist after the end of the universe. Not in the next universe, or the Void, in a by then non-existent universe. It worked.
"Planet of Evil": Zeta Minor, where strange beings lurk and try to prevent catastrophe caused by removing material from the place.
"The Impossible Planet"/"The Satan Pit": The titular planet is the prison of a being that claims to be the ultimate source of evil in the universe, and indeed older than the universe, and it's parked in an unnatural orbit around a black hole.
"Utopia" has the Doctor travel to near the end of the universe, finding desperate humans trying to flee from the vampire-like Futurekind.
"The Doctor's Wife": House is particularly eldritch, being a sentient asteroid living in a pocket dimension that feeds on TARDISes.
"It Takes You Away" introduces the concept of an "antizone", a between-space created at points in time and space where reality is under terrible threat. The one the Doctor and companions enter is a dark maze filled with flesh-eating moths, populated by a mysterious alien who somehow managed to enter such a place. In this instance it exists as a buffer zone to what's called the Solitract, a sentient plane of existence so eldritch that the universe couldn't form until they were separated and remain separated on all levels.
"Spyfall": The home dimension of the Kasaavin is a dark, misty realm filled with an endless forest of cables. The Doctor's encounter with Ada Gordon there indicates it's also a Place Beyond Time, since Ada is coming from 1834 while the Doctor was just teleported from 2020. And the only known way to get in or out is to somehow get the Kasaavin to do it...
In Fargo the stories are spread over a large Midwest area consisting of Minnesota and the Dakotas. They are shown in a perpetual state of winter, and the area attracts an unseemly amount of gang violence and brutal crime. It also attracts flying saucers and an assassin implied to be the Devil himself, and contains a bowling alley that may be a portal to the afterlife.
Einstein's Realm in Farscape. Reachable only by wormhole, it acts as a meeting ground between the representative of the True Ancients and anyone knowledgeable enough to be dangerous to them: it's basically an iceberg floating in an ocean of wormholes beneath a pitch-black sky. Due to Einstein's influence, physics tend to behave quite strangely here, and Crichton often ends up speaking to long-dead individuals from his past and tumbling into Unrealized Realities.
The town that the series takes place in is one of these. People arrive in it on the same road from different locations all over the country, it's a Closed Circle that can't be exited once entered, all the buildings have power despite the lack of a power grid (or even actual wires in the power cables), and of course, there's the monsters that come out every night from tunnels under the town to kill everyone they come across.
The forest surrounding the town as well. The monsters emerging from it every night already makes it supernatural, but exploring it just brings up more mysteries — on his first extended exploration, Boyd discovered a ruined structure composed of stones that repel the creatures from buildings when hung from a doorway. Later, he and Sara find their tent moved by something overnight, ending up in a grove covered in giant spiderwebs, wherein Boyd sees what appears to be his dead wife suspended in a cocoon, before they later stumble across a giant lighthouse. And there's also the matter of the farway trees, large hollow trunks that will teleport whoever enters them to a random location.
Game of Thrones: The Land of Always Winter, beyond the Wall. The stories told about it and the fact that it's the home of the White Walkers is bad enough, but when Jon and his team actually go there, they quickly find that it’s completely and utterly dead; there’s no plants, no animals, no people... just endless plains of ice and snow, dotted by the occasional frozen lake and aimless wight. The sun never shines through the clouds and the snowfall never stops, like a hellish version of Antarctica in the winter. Worse, it’s implied that the White Walkers are trying to make it spread; Dany and Bran both have visions of a Bad Future where the White Walkers win, and in both Westeros ends up looking just like the Land Of Always Winter. And when the Night King attacks Winterfell, he brings a massive snowstorm just like those beyond the Wall, which only dissipates once he’s killed.
The Haunting of Hill House (2018): Hill House itself. Anyone who stays on the property after dark is likely to see or hear somethings, and for the psychically sensitive things are worse. Anyone who dies on the property stays there as a ghost, and the Red Room, the house's "stomach", lures people to their deaths so they can stay in it forever.
Of a light-hearted vibe, Llan-ar-goll-en has the titular village, a close-knit village with malicious pirates and magic wizards, Everything Talks including animated animals and hand bags, singing letter stamps, and everything always goes missing on a daily basis.
The Lord of the Rings: The Rings of Power: Sauron's fortress in Forodwaith is a prime example of an Evil Tainted Place. By the time Galadriel finds it, it's been abandoned by centuries, but whatever evil Sauron did there is still there. The place is infused with black magic, corpses of Orcs are literally melted on its walls, and the fire from torches can give any heat at all.
The eponymous hotel room of The Lost Room, more so the area around where it is supposed to be, including the room that (was?) next to it.
Mako Mermaids: An H₂O Adventure: The Trident Chamber, an endless underwater area where the trident was sealed. There's no bottom, no surface, no visible source of light, and no other features besides the trident itself floating just beyond the portal needed to enter it. Even worse, the Merman Chamber's security system will teleport any unapproved users into this place, where, human or merfolk, they'll eventually run out of air. Evie, Ondina, and Erik were all trapped in there at separate points in the series, with Erik and Evie both making it clear they thought they'd die in there (Ondina was unconscious for the most part).
The Valley of the Fallen Kings in Merlin. The first time we see it, it's revealed that the Crystal Cave, the source of all magic, is hidden in the valley. And is also a very good example of Good is Not Nice, as it's perfectly willing to subject Merlin to Mind Rape and a chain of Self-Fulfilling Prophecies to teach him a lesson. Arthur constantly says that the Valley is harmless unless you're superstitious, but even he and the Knights avoid it if they possibly can.
The Dark Tower, very much so. In addition to the stories young knights are apparently told to scare them away from it, it is surrounded by a forest that, in addition to being nigh impenetrable, reverses directions so you can only get out if you have help. It also looks rather terrifying and Queen Mab gives Merlin some rather disturbing advice:
Queen Mab: You must beware, Emrys. The Tower is not a real place. It is the heart's rest, the mind's deepest fear, the stillness in the hummingbird's eye.
And this was before we knew what it did to the people that the High Priestesses brought inside: it tortured them until the screams could be heard from twenty leagues away and then bound their spirit, leaving their body an empty vessel for another's will to inhabit. The process is nightmare-inducing, and we get to see it all from Gwen, the victim's, perspective.
Room 104: The motel room itself appears to be one, attracting all manner of bizarre and downright supernatural events; the motel's first owner murdered her brother on the site that would become the room, resulting in her (and the ground) being cursed by a frightening, inhuman being.
The titular Lost Galaxy from Power Rangers Lost Galaxy is this. Technology doesn't work correctly (Terra Venture's navigation systems can't even tell which way is up!), clocks run backwards and plants age in reverse. Then there's Captain Mutiny, who begins to capture slaves and attempts to plunder Terra Venture. The only way in or out was through the equally mysterious Galaxy Book.
The Q Continuum, home of the (supposedly) omnipotent and omniscient species known as the Q (and also sometimes used as a name for the species itself). When we saw it on-screen in two Voyager episodes, it appeared first as a gas station on a desert highway and then as a battlefield from the American Civil War (when the Q were fighting their own civil war). This was probably done due to the show's budget constraints, and was justified by explaining that the Continuum cannot be perceived by a humanoid as it truly exists, and thus it will appear as an analogue from the viewer's culture. In one TNG novel, the android Lt. Commander Data is taken to the Continuum and forced to perceive it in its true form. This causes him to shut down as the result of the sensory overload.
Another Star Trek example is the Next Generation episode "Remember Me," in which an experiment with warp bubbles goes wrong and sucks Dr. Crusher into some kind of parallel dimension shaped by the thoughts she was having at the moment she was trapped. It appears to be a replica of the Enterprise, except all the other crew members start vanishing one by one and no one except Crusher remembers they existed. Then it gets even worse. Dr. Crusher activates a view screen and sees a "warp energy field" encasing the ship. After establishing that there is no penetrating the field, she asks the computer to define the universe. It replies, "THE UNIVERSE IS A SPHEROID REGION 705 METERS IN DIAMETER". The computer says that there is nothing outside of the ship.
Just before asking that question, Dr. Crusher asked the computer the diameter of the energy field surrounding the ship was. The computer replied that it was 715 meters in diameter. That is not a typo; the field had shrunk 10 meters between questions, and continued to shrink throughout the episode.
Crusher spends most of the episode thinking she's going insane, and with everyone around her apparently certain she is (until they disappear, that is). The turning point occurs when, after exhaustive tests show nothing wrong with her brain, it finally occurs to her: "If there's nothing wrong with me, maybe there's something wrong with the universe."
A prior episode, "Where Silence Has Lease", does this with a Federation starship — or, more accurately, an illusion of the USS Yamato, a sister ship of the Enterprise. While on The Bridge, Riker and Worf open a door — that leads to the bridge, and they see themselves on the duplicate bridge. This, naturally, confuses the hell out of Worf.
"There is one bridge! One Riker, one bridge!"
From Star Trek: Voyager, there's Fluidic Space. It's an extradimensional realm where there are no stars or planets or anything else of mass. Everything is just a organic soup there. The only life form that has ever been encountered there is the equally eldritch Species 8472, which the Borg consider the apex of biological life.
Another episode has Voyager trapped in a phenomenon called "chaotic space," which is inhabited by aliens that can't be seen directly and can only communicate with certain people via hallucinations.
And at one point, they become trapped in a stellar phenomena known only as "The Void", a weird fold in space without so much as a micron of matter inside. Ships drawn in survive by raiding other ships.
Season 3 of Star Trek: Enterprise takes place in the Delphic Expanse, a region infamous for inexplicable anomalies and even large areas that aren't entirely in this universe. This is revealed to be the work of aliens from another realm who are altering the galaxy to suit them; once they're defeated, the Expanse turns into normal space.
The Upside Down in Stranger Things, a bizarre, hellish, and desolate Dark World version of Hawkins that is covered by a living Meat Moss, home to demonic beasts called Demogorgons, and ruled over by the Demogorgons' dark masters, the Mind-Flayer and Vecna, who seek to break down the dimensional barriers between the Upside Down and Earth in order to conquer the world. It used to be even more eldritch, though — ironically — less dangerous, having been seemingly just a shapeless plane of energy inhabited by an unthinking Hive Mind. Unfortunately, the arrival of Henry Creel/Vecna gave it something it didn't have before; human intelligence and drive… specifically the intelligence and drive of murderous Super Supremacist sociopath, with all the horrifying results that implies.
Every human's heaven is a Lotus-Eater Machine, basically just the best moment of your life over and over again but in all but a few rare cases involving soul mates, your loved ones are merely projections. In the Series Finale, Jack reorganizes Heaven so everyone can be with their loved ones.
Purgatory is a dimension where monster souls go when they die. It's a forested place where all creatures live in a state of hunting or being hunted. Food and sleep don't seem to be a thing, just hand-to-hand combat. It's considered particularly hostile to angels and humans but Dean Winchester thinks of his time there as pure. Castiel, on the other hand, suffers greatly but refuses to leave because he feels it necessary to do penance for his past actions.
The Empty is a dimension outside our universe and understanding where angels go when they die and exist in a perpetual sleep state. It's also sentient, and it becomes annoyed with Castiel for not sleeping.
The Twilight Zone (1959): In "Little Girl Lost", the other dimension to which Tina Miller is sent is a bizarre, abstract realm which distorts perceptions. For instance, Tina's father Chris believed that he was standing upright in spite of the fact that his legs were still on the other side of the portal.
The Red Room. A world where people speak backwards, time works... differently, and the resident Spirits feed on human pain and sorrow. The lodge itself is really just a series of identical rooms with red curtains and a zig-zag patterned floor. Or it could be that it is just the same room repeated over and over. It is either the Black Lodge itself or a place between the Black and White Lodges.
The Room Above the Convenience Store. The apparent meeting place of the Lodge Spirits, implied to be a time loop of the exact moment the Trinity Nuclear Explosion occurred.
The Black and White Lodges. The Black Lodge (beneath the floor of the Red Room) is an infinite sea of stars with a single floating "room" where time works... wrong. Meanwhile, the White Lodge is a massive fortress in the middle of a purple ocean that stretches beyond the eye can see.
The Return continues to add places like the inside of a nuclear explosion.
Several locations and objects create a connection to the supernatural world including The Palmer House, 2240 Sycamore, Glastonbury Circle, Jack Rabbit Palace, and The Dutchman. They all open portals to other dimensions or are frequented by Lodge Spirits, warping them in some way or another.
," in which an experiment with warp bubbles goes wrong and sucks Dr. Crusher into some kind of parallel dimension shaped by the thoughts she was having at the moment she was trapped. It appears to be a replica of the Enterprise, except all the other crew members start vanishing one by one and no one except Crusher remembers they existed. Then it gets even worse. Dr. Crusher activates a view screen and sees a "warp energy field" encasing the ship. After establishing that there is no penetrating the field, she asks the computer to define the universe. It replies, "THE UNIVERSE IS A SPHEROID REGION 705 METERS IN DIAMETER". The computer says that there is nothing outside of the ship.