"The Mystery of Nature" National Natural Monument

The cave is a sea cave (sea cave) made of basalt cut, and it is called "Nanatsugama" because of its appearance in seven rows, making you feel the wonders of nature.
Those with rock surfaces lined up regularly like pillars are called columnar joints, which shrinks when lava cools and hardens. The largest hole has a frontage of 3m and a depth of 110m. If the wave conditions are good, you can get inside by pleasure boat. In addition, on a sunny day, you can also see the neighboring island of Iki, Nagasaki Prefecture from the observatory.