Aflutter with bats, and with stalactites dripping from the cave mouth, Domica is more than just another eerie grotto. Open to visitors since 1932, this is the largest cave in Slovak Karst National Park and it enjoys protection as an underground wetland. Guided tours lead visitors in among the spindly rock formations of this humid cave, including an atmospheric boat ride. It's very close to the Slovakia–Hungary border, just south of Dlhá Ves.
Sixteen species of bat are at home in its 1km-long passageways. Discovered in 1926, the cave sparked great excitement when early Stone Age fragments were found within.