This includes the Mountain, Sandcliff and Snow biomes. A player can pave these terrains, but cannot perform any other landscaping, including stomping the paved tile down to the original surface.
Paving/stomping works fine in caves, so I assume it's a bug. A player cannot use Survey to raise or level these three terrains either, so while a player could pave and build something on these terrains it's unlikely. There might be a work around; I've seen a farm built on mountain terrain using dirt and plowing. I don't know how it was made and I haven't been able to reproduce it.