Alternate Versions of Inifinite Worlds

[Culture20]

Originally Posted by SilvercatMoonpaw

That would certainly keep them out of reach of civilizations below a certain TL, which is a neat idea. Though the ease of running ground transport through ones at dirt-level is probably better for interconnecting worlds.

Then underground or undersea. A new tunnel in NYC for a subway line happens upon a portal and it’s only open when the other world has dug there. Even more concerning when the second world’s digging crew suddenly finds a subway train full of people in their newly dug tunnel.

Or to take a page from Planescape, perhaps the portals require a particular key to activate; a substance, signal, sound, particular thought, etc.