We are game developers. We don't have to abide to the rules of this universe. We are above realism, we are above all human passions and desires. And put a pit of fire after the door, before the treasure room itself with a floating platform going back and forth, being moved by an unknown force. Korlok teleports to Moonshine.
Crypt collapses, and so does the snowy mountaintop.
In its foulest form, a dungeon is nothing more than an indoor scenario, randomly created with hallways and rooms filled with traps, treasure and monsters. The complex is located in an isolated region where it rests untouched, until a fearless group of looters er, I mean, characters shows up to ransack it. Credit where credit is due, modern CRPG dungeon structures is my favorite topic of conversation for barbecue talk. After all, that's the question developers are supposed to ask themselves. See, that's called improvement by experience.