Welcome to Hub!
Our fair city is round, and split into boroughs. Each Fandom has it’s own borough here in Hub. And while a person from one Universe might share a borough with a person from the same Fandom but a separate Universe, that doesn’t necessarily make them the same. Curious? Then by all means, stay a spell and read on!
The space around hub is filled with mist. The ‘walls’ aren’t solid, but rather a subsiding of the mists, allowing the city to exist. The city expands as needed, growing outwards slowly, almost imperceptibly, the mist pulling back to accommodate the growth. A person can walk into the mist, but they will find that they can’t really go anywhere. There is simply nothing in the mist.
Every borough in Hub is the same size, even if they aren’t. If you measure it, they really are. If you’re trying to get through any one borough, say to get to the next, it will always take one hour, regardless of which borough it is, how many people are there, etc.
The buildings, all of them, are bigger on the inside. It’s inexplicable to most, others think they understand it via technology or magic, but no one really knows which it is (if either) for certain.
Hub, and all of its buildings, landmarks, foliage, etc are self-healing. Buildings and such take an hour or less to regenerate. They only regenerate original items to the fandom. If you live within the Star Trek borough and you had set of nearly mint condition (just some slight foxing around the edges) Captain America cards that were destroyed when Voltron attacked the borough, well, those are gone, sorry. This does mean that anything from a foreign fandom is lost if it is destroyed.
Everyone in Hub can breathe, eat, and talk. Make of it what you will. Everyone experiences Hub in their own way. Just because you experienced something here doesn’t mean everyone, or even your character, will experience it that way in the future.
Is Hub magic? Is it just amazingly advanced tech? Maybe it just operates under different laws of nature. No one knows. No one.
There are no actual natives of Hub, but there could be people who don’t remember where they came from anymore.
Anchor characters, and those who bring in new landmarks with them, have the option to populate the landmarks and boroughs with NPC “echoes” - these are “non-canon” and in the event that these people ever arrive in Hub, they are replaced with the ‘real’ version of themselves. The incoming character will never be under any obligation to accept, live up to, or acknowledge what their echo did.
Oh, one last thing! The portals!
Everyone knows about the portals, don’t they? No? Wow, you must be really new then!
Each universe has at least one portal. Even the universes that haven’t been discovered yet. Even the universes that haven’t established a borough! Of course, the portals don’t really always appear like a… Portal. Sometimes you’re thrown through and you don’t even realize what happened. Sometimes you walked through it without realizing it… And still other times you know exactly what you did. Anchor characters set the location of one portal. They know where it is both in Hub and in their universe. Non-anchor characters don’t necessarily have this knowledge, and characters who aren’t anchored definitely don’t. Of course, portals can be found, too, so there’s always that!
Portals are pretty much the size they need to be to allow a person through. Going through to Hub, a portal will accommodate pretty much anything, and allow it to return to its own universe, but going through to a different universe things need to be more people sized, and even then technology, magic and the like don't necessarily always work...properly.