Ryusendo Cave

Ryusendo Cave is considered one of Japan's three largest limestone caves and, along with the bats that live within the cave, is designated a national natural monument. The known length of the cave is 4,088m, of which 700m is open to the public. Eight underground lakes have been discovered, of which three are open to the public. Investigations are still ongoing, so many parts are still unknown, but the total length is said to be over 5,000m.