One of the greatest limestone caves in Japan located by the foot of Akiyoshi plateau.

24m high entrance, 8m in width. The most spacious area inside the cave reaches the size of 200m, 40m high to the ceiling, and 80m high at the highest point.

It is said that the extension continues for 10km, but the only first 1km is open to the public as the general tour route.

The temperature inside is kept to 17 degrees throughout the year.