Portal Door

We know you can replace the arm Data, but you still shouldn't stick it in weird places!

This is a door that opens to a location other than the one behind it; in time, space, and even outside of it! This door may be a Cool Gate, but it can be of much more mundane make and manufacture.

How does this door bend space and time like a Dali painting? It may be a technological teleportation device, a Time Machine (or both). It could also be made through magic (which usually justifies it being otherwise mundane looking), and may lead to the Magic Land, Spirit World or Dark World. Lastly, it may be some form of "naturally" occurring gateway of Eldritch origin that leads to an Alternate Universe.

See also Cool Gate, Portal Network, Portal Book and Portal Pool. Sub-Trope of Teleporters and Transporters.

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Examples:

Anime and Manga

• Bleach: The Gate To Hell.
  • Bleach also had a gate (that looked like a big sliding door) that Soul Reapers could create to travel from the world of the living to the Soul Society (Captain Kuchiki uses one early in the series to return himself, Rukia and Renji).
• One of Doraemon's recurring tools is the "Anywhere Door", which when walked through brings you to any location you tell it, as long as you made sure you worded your request carefully.
• The door leading out of Howls Moving Castle.

Card Games

• The Yu-Gi-Oh!! TCG happens to have multiple takes on this, including 'Different Dimension Gate', 'Monster Gate', and even a card meant to restrict attacks, "The Dark Door", which takes the form of a Cool Gate (or at least a door out of a very freakish universe).

Comic Books

• The Authority can call the Carrier for a Door to anywhere in the world, or back to the Carrier, and at least once to parallel universes.

Film

• The Matrix Reloaded. The doors that can open to different locations depending on which person or key opens them.
• Done in Monsters, Inc. with the doors that serve as portals from the monsters' office building to the bedrooms of children they're supposed to scare.
• Beetlejuice. Following the instructions in a book, the ghostly protagonists use chalk to draw a door on a wall, open it and walk through it into the afterlife bureaucracy.
• Likewise in Pan's Labyrinth, in which Ofelia uses a piece of magical chalk to create a door to the Pale Man's realm.

Literature

• Dan Simmon's Hyperion overcomes the problem of space travel and communication with two different systems. The space travel system is essentially portals. Some very wealthy homes consist of rooms on different planets connected by these portals.
• In Neil Gaiman's Neverwhere (book and show), Door and her family can open up doors anywhere. Their home is a bunch of unconnected rooms.
• The door in Dan Abnett's Ravenor, a plain wooden door that opens through space and time. Originally, it used by special trained operators, to let the questions of those who came to them direct it; when the house was broken, Ravenor operated it to put his powerful psionic abilities into play.
• Susan Cooper's The Dark Is Rising series. Powerful Old Ones (such as Merriman Lyon) are able to summon a magical gate (which looks like a pair of doors) that allows travel through time and space.
• John DeChancie likes this trope; his Castle Perilous has 144,000 doors, each leading to an Alternate Universe, and they don't just wait for you to walk through—the portals wander, and actively seek out those who want to travel or get away. His Skyway series has "Tollbooths" (no doubt named as a Shout-Out to The Phantom Tollbooth) which use miles-tall columns of virtual particles to create wormholes linking a vast Road across thousands of planetary surfaces.
• In The Redemption of Althalus by David Eddings, the protagonists live in a house with as many rooms as they like, as large as they like (they occasionally have armies on the march through the corridors) and can open doors to literally anywhere on command. One of the protagonists attempt, out of curiosity, to open a door to "nowhere"—although they avert the attempt before they succeed, the concept is enough to freak out their patron goddess something fierce.
• The door leading out of the title castle in Diana Wynne Jones' Howl's Moving Castle.
• The redstone doorways in The Wheel of Time look like empty doorframes, but walking through one will transport you to a dimension populated by weird aliens who see the future or grant wishes.
  • The Wheel of Time has them in at least three flavors: the aforesaid redstone doorways, the Waygates built of finely carved white stone and having nice reflection visual effect, and the One Power-created Gateways for Skimming (travel via subspace) and Traveling (instant teleportation).
    • There are also Portal Stones, which are Exactly What It Says on the Tin. They link not only to other portal stones in the world, but also to Portal Stones in Parallel worlds. Very handy, if not well understood at all.
• The title tollbooth of Norman Juster's The Phantom Tollbooth.
• The Forgotten Door by Alexander Key. An inter-dimensional machine/gate.
• The appropriately-named Gates in Mercedes Lackey's Heralds of Valdemar series. They have a number of important limitations, in that they are single-use constructions created by a powerful mage using his own life force, and can only go somewhere said mage has been to and knows well. The ancient Adepts of the Mage Wars, as well as the mysterious Eastern Empire, on the other hand, knew/know the secrets of Permanent Gates, which once created are simple to activate and use.
• In Patricia A. McKillip's The Bell at Sealey Head, Emma keeps opening doors and finding Princess Ysabo. She never dares go in for fear that she can't come back. And one day when she opens the door to her grandmother's room, it shows the princess in a different room. She closes it, reopens it, and finds her grandmother's room.
• The Green Door in H. G. Wells' short story of the same name.
• One means of getting around in the endless world of The Neverending Story is The Temple of a Thousand Doors (Der Tausend-Türen-Tempel), which contains an infinite number of five-sided rooms with three doors each. Every door different in colour, shape, material etc. To get to the place you wish to go, you only need to pass through the rooms until you find the door that reminds you strongest of the thing/place/person you're looking for. This may take some time.
• The portable door in The Portable Door by Tom Holt. A door-shaped sheet of something that can be rolled up, but when put against a wall will open to the desired location.
• In Stephen King's The Dark Tower, Roland discovers a series of doors which allow him to look into other worlds, possess a specific individual on the other side when he steps through the door, and pull that person back through the door into his own world. This is how he eventually gathers his three traveling companions who follow him in the later books.
• Doors that open to distant locations, times, and/or realities are a dime a dozen in the Nightside series, and one minor character even operates a business where people can pay to pass through any of the hundreds of Cool Gate doorways he's stocked his shop with.
• In the last volume of Labyrinths of Echo, Max and Melifaro end up in a magical reality where all doors are this for them: stepping through any kind of portal or door (even self-constructed) transports them to another world (seemingly) at random. When they finally make it back to Echo, Max discovers all doors still continue to function like portals to random universes for him, so he has to condition himself to check every doorway he passes through for this effect.
• In Harry Potter and The Order of The Phoenix during the battle in the Department of Mysteries, Sirius Black gets pulled into an ominous veiled archway after being cursed by Bellatrix. And he hasn't been back since...
  • Frankly, Sirius thought the trip was to die for.
• In The Chronicles of Narnia: Prince Caspian when Aslan sends the four Pevensies home and some of the Telmarines to the deserted island their ancestors came from through a door made of 2 vertical sticks and a horizontal one on top.
• Professor Chronitis's time-travelling study in Dirk Gently's Holistic Detective Agency appears as a door in a convenient wall, or cliff face.

Live Action TV

• The key in The Lost Room can turn any door with a tumble lock into this.
• The Star Trek: The Original Series episode, "All Our Yesterdays" has the Atavachron, a machine that creates a portal door/wall to a time in that planet's past.

Tabletop RPG

• Planescape has Sigil, the City of Doors, which is pretty much made of this trope, though all "bounded spaces" can be portals, so not all the portals in Sigil are actual doors.

Video Games

• Disgaea's dimensional gate warps the user to the selected location.
• Kingdom Hearts has lots of them. Most notably the door to the heart of all worlds. It's a game in which the main character wields a gigantic key. Doors tend to be prominent.
• The Legend of Zelda Twilight Princess features accessing The Temple of Time through a door with a black-and-white entry. This is extremely out-of-place, because the only other time the black-and-white happens in the series is in The Wind Waker when initially traveling to Hyrule.
• Star Ocean Till the End of Time features the main hero Fayt Leingod's high level move, Dimension Door. This attack not only allows the player to teleport behind the enemy and strike, but holding the attack button can damage and potentially stun opponents.
• The room doors in Silent Hill 2's nightmare hotel.

Webcomics

• In No Rest for The Wicked, it's surrounded by crows, it has to be dug up, it's an ordinary door—flat in the ground; and when they open it, it draws November and Clare in.
• In Dream Catcher due to running in between the two worlds, Riza gets plenty of use out of a couple. One being a door, the other being the dreamcatcher.
• In the comic Flipside, creating a portal involves slapping a door-sized piece of enchanted paper on a surface.
• This is how Merlin's time machine appears in Arthur, King of Time and Space; a heavy wooden door in the nearest available wall.

Mordred: Sire, the other side of that wall is the exterior hull of the ship and open space. Where did that door lead to? Arthur: Everywhere.

Web Original

• The SCP Foundation has several:
  • SCP-004, a door and set of twelve keys, which opens to a different place depending on the key used to unlock it. One key leads to a room of seemingly infinite size, one leads to an Eldritch Abomination which destroys the mind of anyone who sees it, while the other ten lead to Alien Geometries which are instantly fatal to human life.
  • SCP-249, which connects to a different random nearby door every time it's used.

Western Animation

• The Simpsons: In a Treehouse of Horror episode Homer finds a portal to the "third dimension" behind the bookcase.

That's weird, it's like something out of that twilighty show about that zone.