Cave of the Lakes
The 55th longest cave in the world
2km · Length
The Cave of the Lakes (Spilaio ton Limnon), formerly called Troupisio, is located near the village Kastria in the municipality of Kalavryta, Achaea regional unit. It is 17 km (11 miles) from Kalavryta and 9 km (6 miles) from Kleitoria. The cave is an old subterranean river consisting of three levels. During the winter when the snow melts it is transformed into a flowing river with waterfalls. During the summer, it dries up, leaving behind 13 lakes.
Cave data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).