A while back I visited a cave with a large room that had been previously used some sort sort of public gatherings. The room was rather wide with no supports in

A while back I visited a cave with a large room that had been previously used some sort sort of public gatherings. The room was rather wide with no supports in the middle. A local official had expressed concern that the room was unsafe and could collapse in an earthquake. The cave operator informed that official that the cave room had been just like that for millions of years, and it was probably safer than any above ground building.