Nanatsugama

"The Mystery of Nature" National Natural Monument

The cave is a sea cave (sea cave) made of basalt cut off, and it is called "Nanatsugama" because of the appearance of seven rows, making you feel the wonders of nature.
Those with regular rock surfaces like pillars are called columnar joints, which contract when the lava cools and solidifies. It is the largest hole with a frontage of 3m and a depth of 110m. If the wave conditions are good, you can enter by sightseeing boat. In addition, on a sunny day, you can overlook the neighboring island of Iki, Nagasaki Prefecture from the observatory.