This is more a philosophical musing than an actual question, but I was thinking about if a continent could be a mega dungeon, if there was a set or established path through it? Is the interstate highway system running across america just a multibranched megadungeon? Is the Trans Siberian Railroad a solid map for a megadungeon? Just thinking about and experimenting with form a bit! What do y'all think?
Here's my thoughts on it.
We can start by defining a megadungeon as a "dungeon" that is "mega". Mega is easy to define: it basically means bigger or more intense than typical. So a megadungeon is a bigger, more dungeon-ey dungeon than usual.
Dungeon is much harder. I would describe a dungeon as any self-contained adventure location, with a clear distinction as to whether you are in the dungeon or not. It doesn't necessarily need to be a single contiguous structure, or even inside, but if the edges of a dungeon aren't clear, what makes it different than just a location. Which is also why the traditional oldschool dungeon has been a literal dungeon - because you don't get much more clearly defined than "in rooms underground" and "anywhere else".
I've tried to be pretty loose with the definition here, but there's a lot of boundaries that can be pushed.
Can a megadungeon be multiple related locations? I don't see why not, so long as they're distinctly part of the same thing. For example, what if a spaceship broke up in orbit, and the party had to traipse around a country or world to explore the varying fragments. At high levels, these disconnected chunks might not even matter, as the party can teleport between them freely.
Can a megadungeon be totally disconnected? It's a bit outside what I would define a megadungeon, but I'm sure people with different insights than me could make it work. Like your description of Interstate being a megadungeon. Would different offramps be encounters? Would encounters be on the road or off?
Can a megadungeon be small? Mega doesn't have to mean big, it can mean more. More dungeoney. More encounters in a single room. The party never travels more than a hundred feet from the front door, like an escape room on steroids.
And all of this is limited to my preferred RPG style of sword and sorcery style adventuring. What about a heist megadungeon, where a group of runners has to descend into an ever-more complex series of vaults?
What about a social megadungeon, like some kind of elaborate diplomatic event, where the party can't draw their weapons once, and has to schmooze through many layers of social nicety, and keep track of the growing web of interpersonal relations. That would be fascinating to read, but I suspect way beyond me to write or even run.
