Reading the Italy rough guide book informed me that there is a large network of caves below Orvietto, so we enquired about visiting that today. We were just in time for a guided tour, and quickly joined up.
The tour was ok, not as spectacular as I had hoped, but interesting nevertheless. I suppose my expectations to see lots of the cave network could not ever have been realised, and the few we saw on the tour were interesting.
Apparently lots of the houses and shops have caves or networks of caves below them - how cool. I think if I was building again I would definitely specify at least one cave!