Nanatsugama

"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 the appearance of seven rows, giving you a sense of natural wonders.
If the rock surface is lined up regularly like pillars, it is called columnar joints, which shrinks when the lava cools down and hardens. 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.