Belletor's Folly is a mine located south of Kvatch. It is south of Kvatch proper, but directly west of the location "Kvatch", close to where the road from Anvil forks to go towards Kvatch, northwest of Dasek Moor.
In the third level, named Belletor's Folly Cavern, there is a room with a trench in the middle, and a bridge crossing the trench. But both entrances to the room leads into the trench, and there seems to be no way to get up into the room. There are a lot of bandits (and at least one ghost) in the room above, but no way for them to have gotten up there. There is a conspicuous-looking vine hanging from the ceiling down to the bottom of the trench. One theory is that the vines were originally meant to be climbable, and that this cave is still designed with this assumption.
Bandits with leveled armor and weapons