These underwater caves are said to have formed over 200 million years ago (during the Paleozoic Era)! They became submerged in water around 83,000 years ago due to a large volcanic eruption from Mount Aso in Kumamoto. The caves are full of natural structures such as underwater stalactites, corallite, (fossilised coral), bell-shaped structures on the ceiling, and helictites (stalactites that grow out horizontally or diagonally and can look like twigs or branches). There are also deep pools, some of which are deeper than 40 metres, and clear streams.
The path through the caves is illuminated and is 350 metres long. You can enter the caves all year round, as they have a constant temperature of 16 C, making them feel refreshingly cool in the hot Kyushu summer, and warm in the winter.
Opening Times 9:00 - 17:00 (normally extended in Summer)
Admission Fees Adults: 1,300 yen Junior high and high school age students: 1,000yen 4 years old to elementary school age students: 700yen