Last dungeon-crawl I ran involved rescuing a couple locals from a dragon in an earby pyramid, meanwhile fighting off the undead residents of the lower stories, reconstructing the events that led to the death of the original inhabitants, eventually confronting the dragon with the fact that it was the coalesced nightmare of a dead wizard, and venturing into the dream-realm version of the pyramid to confront that wizard and lay his spirit (and the dragon) to rest.
What made it a dungeon-crawl from my eyes:
-Lots of combat, about two or three times as much as I usually have in a game.
-Choices sharply limited, for the most part: go this way or that.
-Areas divided into levels, with the later levels more difficult than the earlier levels (in this case, the levels were very short, and got shorter as they ascended the pyramid).
-A trap or two.
-A variety of enemies.
Daniel