Inazumi Underwater Cave

Inazumi Underwater Cave is the longest underwater cave in Japan, and can be found in the southwestern area of Oita prefecture.
Throughout the year, the cave is around 16 degrees Celsius. The cave has many fascinating sights, such as icicle-like limestone structures.
At the Cave Museum, visitors can learn about the underwater cave’s structure through videos and exhibitions. Both children and adults can have a fun learning experience at the museum.
There are fun events around the cave as well, such as the Firefly Festival held in early June. During the time of the festival, fireflies can be found in the area.