A world that contains access to many others, most of which are themselves unaware of the existence of portals/other worlds.
Where the Portal Crossroad World is populated and has widespread portal travel, expect the culture to be a strange mishmash of elements from other worlds.
Compare Portal Network, more often found in sci-fi where many worlds are equally interlinked by a portal transport system; contrast Void Between the Worlds, the space through which the portals pass. Also compare Inn Between the Worlds, the single-room/building version which is itself outside reality. See also Extra-Dimensional Shortcut.
This is a common form of the video game mechanic, Hub Level.
- In The Incredible Hulk Issue #300, Doctor Strange sends a mindless rampaging Hulk to the "Crossroads," where all the worlds join, allowing him to choose the world he wants to live in. In case he enters a world and isn't happy there, Strange places a subconscious trigger in the Hulk's head to send him back to the Crossroads again.
- Nightcrawler teleports by travelling through a parallel dimension. The black smoke he leaves behind while teleporting is that dimension's atmosphere.
- In the Magical Girl Crossover Shattered Skies: The Morning Lights, the Lighthouse is a crystalline structure in interdimensional space that works like this. Refugees from five different parallel universes are brought there to escape the destruction of their homes.
- In The Institute Saga, Earth becomes this in an inter-reality basis, resulting in the other realities taking numbers based on which Dome their Gate is in while as the central reality, Earth becomes Universe Alpha.
- Treasure Planet itself is a planet-sized portal generator created long ago that was discovered by pirate Captain Nathaniel Flint. Flint used the portals to surprise merchant ships and plunder them ruthlessly, then store the captured booty on the centroid of the portal mechanism. This was how Treasure Planet got its name.
- In The Nightmare Before Christmas, a grove of trees with holiday-themed doors provides passage between Halloween Town and Christmas Town.
- Contact has Hyperspace Lanes from many worlds all leading to the one place where the aliens bring new sentient species to introduce themselves.
- Sakaar from Thor: Ragnarok is a planet surrounded by thousands of portals from across the universe, many of which appear and disappear at random. Blind FTL jumps and other errors during teleportation can lead to you being dumped there. You can use the portals to leave, but that's easier said than done when the planet's ruled by an immortal, questionably sane tyrant who really doesn't want anybody to do so.
- The city of Scalentine in the Babylon Steel novels sits at a planar convergence and has portals to several other worlds. As a byproduct of the meeting worlds, most magics are nerfed while you're in town.
- The Chronicles of Narnia: The Magician's Nephew has a universe/dimension referred to only as "The Wood Between the Worlds". It's a forest that stretches as far as the eye can see, dotted with pools of ankle-deep water. With the proper magic (such as the rings created by Digory's uncle) these pools become a portals to other universes, like our Earth or the land of Narnia. To prevent malicious exploitation, the realm induces sleep in anyone that stays too long.
- In Jim Butcher's Codex Alera, Word of God says that Carna is Another Dimension that has wormholes pop up in other dimensions and suck beings in.
- Crossroad of Nick O'Donohoe's Crossroads trilogy (The Magic and the Healing, Under the Healing Sign, and The Healing of Crossroads). Some inhabitants there can go to and from there at will, but most end up there by mistake. It's very much a refuge of mythological species.
- The Arena in Grand Central Arena, where every spaceship with a drive for Faster-Than-Light Travel ends up.
- Hell's Gate: The titular world, a parallel Earth, contains the largest portal cluster known to the two civilizations exploring the portals, who first encounter each other there.
- His Dark Materials: Cittàgazze's world in The Subtle Knife has many portals thanks to the titular object.
- The Manticore system in the Honor Harrington series sits near a Negative Space Wedgie dubbed the Manticore Wormhole Junction, a cluster of six (later seven) wormholes connecting points hundreds of light-years apart. The Star Kingdom of Manticore's ownership of the junction has made them incredibly wealthy and also grants massive strategic advantages to their military, since they can get their forces around the galaxy much faster.
- In KJ Taylor's first book, The Land Of Bad Fantasy, the protagonist comes from one of these, called Y'hyerd B'zeck. There, interdimensional travel is so common that there are various Advice for Dummies books about it, aspects are taught in school, and there is no semblance of whatever their original culture was.
- The Neitherlands in The Magicians are an intentional variation on "The Wood Between the Worlds" of the Narnia series.
- From Stephen Donaldson's Mordant's Need series, Mordant is this through the use of Imaging and the mirrors. Curved mirrors act as windows to other worlds, according to their shape and exact composition. An Imager is then able to summon what he sees through the mirror and into Mordant.
- The Nightside from Simon R. Green's novel series is a hidden urban center full of Timeslips to distant eras or alternate histories, passageways to alien realities and planes of existence, and Bigger on the Inside pocket dimensions. Characters such as the Doormouse or the proprietors of the Mammon Emporium have actually commercialized this trope, using portals for architecture, transportation, and importation of exotic goods.
- The Quentaris Chronicles: Quentaris, with its rift caves (acts mostly as a one-city-world) is a variation. While many worlds trade through the rifts, many also do not know of their existence. Quentaris also has a greater concentration of rifts than any of the other worlds, which have few or no others.
- In Lyndon Hardy's Secret Of The Sixth Magic, the demon's realm acts as a one-way version as fires in any realm all lead to it. In Riddle of the Seven Realms, the titular question is if all fires lead to the demon's realm, where would a fire in the demon's realm lead? To the Void Between the Worlds, which would destroy all the realms.
- The city of Sigil in Planescape is also known as the City of Doors, because there are gateways to all known and unknown planes there.
- In the Forgotten Realms, one drow city has a whole bunch of portals to various places on the surface, and so is commonly used by raiding parties from various other cities.
- In Eclipse Phase the Solar system has at least five Pandora Gates, which for some unknown reason aren't all capable of dialing into the same systems. Most other systems have one, but the creatively-named Portal has six Gates that are not only on the same planet but clustered within a 1-kilometer radius, while Sunrise has seven Gates spaced equally around its' equator.
- Mortal Kombat: Deception introduced the Nexus, a void-based Hub World of sorts that opens portals to other realms with the use of the Kamidogu.
- Chrono Trigger has the End of Time, a dimension that exists after time is eaten, containing portals to the different eras and can be used to access an early-game Peninsula of Power Leveling.
- Super Mario 64: The paintings in Peach's castle act as portals to 11 of the game's 15 stages note , which Mario has to enter to retrieve the Power Stars.
- Near the end of Bioshock Infinite you will enter one of these and travel around to different Alternate Universes.
- X3: Terran Conflict and X3: Albion Prelude have the Hub, a sector consisting of a giant, spherical space station that can insert itself between up to three pairs of jumpgates, dramatically shortening routes across the gate network.
- The Nexus in Heroes of the Storm is implied to be one, connecting through the universes of various Blizzard games and franchises like StarCraft, Warcraft, Diablo, Overwatch, and even to the classic ones like the The Lost Vikings.
- The Reaper's Realm in Neverwinter Nights: Hordes of the Underdark has doors to several worlds, although you can only use the one connecting back to Toril at first. After Mephistopheles kills you, that door closes and the door to Cania, the Eighth Circle of Hell, opens.
- Napple Tale applies this trope in more than one way. In plot terms, Napple World lies between life and death; in gameplay terms Napple Town is the Hub Level that connects all of the season-themed worlds which the main character must explore.
- Riven has the 233rd Age, which contains linking books to all of Riven's islands, and is the only way to access Prison Island.
- The Quilt in Nightmare Ned, where all 5 nightmare worlds are represented by a symbol on one of its patches. It's subverted in that aside from you being able to instantly return to it at will (at the cost of one of your 8 hours), there are also hidden doorways within the nightmares themselves that can be used as shortcuts between each world.
- Dragon Age: Inquisition has a pocket realm on the edge between the mundane world and the Fade where the ancient elves' Eluvian network had a hub. It's specifically called the "Crossroads".
- A House of Many Doors is the story of a living pocket dimension that steals from other worlds. The three arc questions are: what is this place you were born in, who originally created / owned it, and how do you get out. There's two ways out, but they're kept triple-locked for a reason; the first is the doorway containing THAT Eden. Eat the fruit, and you will be immortal as long as you stay in the house, but an entire random living world will DIE. The second is a breach point made by the original owner when they were locked out and busted their way back in. The breach point is guarded by one of the higher gods, Scorpidithon, and it will break the house apart if it isn't held together.
- The Homeworlds from the original Spyro the Dragon trilogy act as this, having easily accessible portals to smaller worlds populated by other inhabitants.
- In Touhou Tenkuushou ~ Hidden Star in Four Seasons we're introduced to the Ushirodo-no-Kuni (The Land of the Rear Door), filled with many doors that go to every possible place in Gensokyo, it's the setting for the latter half of the game.
- Kaspall gets a lot of people from other dimensions falling through unstable portals, unfortunately they can't seem to go back. There is also a stable Portal Network but it only connects locations within the city.
- Kill Six Billion Demons has the city of Throne, which is heaven, and the King's Doors, which link it to the 777,777 worlds/universes created by the gods.
- Missing Monday features a maze of twisting corridors lined with doors to many worlds.
- The Shadows Over Innsmouth features the city of Yizix, where its many portals are visible in the sky.
- The planet Freleng lies at the center of the galaxy in the Loonatics Unleashed universe, where it functions as a portal junction. Control of planet Freleng is critical to a trio of villains bent on galactic conquest.
- Star Wars Rebels introduces the World Between Worlds near the end of the show, which is basically this. Since it allows not only fast travel via fold space, but also Time Travel, it is very dangerous to use, especially if put in the wrong hands. This is why only select individuals like Ezra, Ahsoka, lothwolves, and Morai can access it, while Palpatine, even while using Sith alchemy, can only stick his hand in. From what is currently known, there are portals on Lothal, Malachor, and Coruscant.