As much as we want thdere to be no interior cells for smooth sailing all along the way, that would be overlag, dont you think?
I mean, I would absolutely love if caves and buldings were all part of one world space. (I of course assume cities to be an exterior cell, because that was a better choice all around)
But the toll that will take on some computers would be harsh.
Not if they were zoned. As in, the first room of the cave or whatever is always loaded, but then the rest loads as you get into the cave. Games as old as Unreal Tournament 2004 used techniques like this to reduce lag. Very different world types, I know, but still, it's something to consider.