There's this curious book I got a couple years ago. "Stone Shelters" by Edward Allen, MIT Press. Not me, he was writing it in the 60s when I was just a kid. Looking the book up, I find he was pretty prolific in architectural books. My copy is old and used, a '74 printing, but I see copies available on Amazon.
Anyway, this other Edward Allen went to southern Italy on a Fulbright in the '60s and studied, photographed, and sketched trullo houses and cave dwellings that stayed in use well into historical times. A trullo is a house built around sort of a beehive dome of unmortared stone blocks. The combination of photos and plans of trulli here are appealing for modeling buildings or doing RPG maps. The cave dwelling maps he provides are fascinating to show the patterns in which cave dwelling people actually carved out caves into homes instead of a gamer's guess. Google image search turns up only one bad scan of his floor plan as part of an architectural essay.
It's worth picking up on Amazon.