No wandering dungeon dragons, certainly. But once when running the old basic D&D adventure Isle Of Dread I rolled a red in a wilderness area. I decided, because this was a fairly big area, they could well stumble across a cave rather than just get attacked in the middle of the jungle. (One guy stabbed it to death somehow. I was rather disappointed.) Anyway, a really big wilderness area, in a hack-and-slash kind of game, that I could understand. Not modern dragons, I don't think - these days I throw in a dragon and expect the PCs to still be wary of its haunts ten levels later.
I now express disbelief and wonder at the idea of any dungeon that could fit wandering dragons.
Oh god. I just had a stupendously creepy idea for a necropolis. Endless fields of eternal rows of coffins standing on end, forming walls ten feet or more tall. The ceiling is much higher. Something really big could walk around putting its feet in individual rows of the fields. That's just freaky.
