Pigeon Hole Cave is a short woodland walk from Cong and one of the best small clues to the strange limestone country around the village. Steps lead down into a narrow chasm where an underground stream runs below the trees, carrying water between the loughs while the surface landscape stays oddly dry.
It is not a show cave, and that is part of the appeal. The visit is quick, damp, and a little eerie, with folklore about white trout and disappearing water doing as much work as geology.