A short, tight limestone cave a few minutes' walk from Mahendra Cave, with a resident colony of horseshoe bats hanging from the upper galleries. The cave is just 150 metres long and not for the claustrophobic — the exit is a tiny squeeze hole halfway along that you can take instead of returning the way you came in.
Take a torch, wear clothes you don't mind getting dirty, and accept that the smell of guano is part of the experience. Local boys often act as informal guides and will point out the bats; a small tip is appreciated. Combine with Mahendra Cave for a single half-day outing.