About the Inazumi Underwater Caves
The Inazumi Underwater Caves were formed 300 million years ago during the Paleozoic era. It took its present form after being submerged by a major eruption of the Mount Aso volcano 300 thousand years ago. Inside the caves are numerous underwater stalactites, coral stones, bell holes, and helictites, making them one of the most unique underwater limestone caves in the world.
It is home to countless stalactites, deep fissures that are more than 40 meters deep, and clear streams of pure water that gush forth from the depths of uncharted caves. The beautiful contrast of the underwater limestone caves, reflecting a multitude of different beauties, leads visitors into a world of fantasy.
The temperature in the caves is 16°C all year round, and it is cool in summer and warm in winter, making it a comfortable space. You can take your time to view the wonderful underwater limestone caves at any time of the year. Experience a moment of healing inside the caves where you can feel negative ions flowing through your body and soul.
Admission fee
Admission fee includes the entrance fee to the limestone caves and other facilities.
General customers
Group tour customers (20 people or more)
Group tour customers (80 people or more)
Customers with disabilities
Admission fee for pets
- ・Admission fee includes the entrance fee to the caves and other facilities.
- ・Group tour customers may dine as a group at Meisuitei. Meal costs start at 1,200 yen.
- ・Buses can be used to enter the facility.
- ・Reservations are required for group tours. Please contact us for more information upon your visit (Inazumi Underwater Caves TEL.0974-26-2468).
Beginning of the Inazumi Underwater Caves
The Inazumi Underwater Caves originated about 200 million years ago. Long, long ago, when the dinosaurs roamed the land and we, humans, were about to emerge, we were about to enter the long, cold Ice Age. It is believed that the original structure of the Inazumi Underwater Caves was formed around that time. Then, about 85,000 years ago, a major eruption of the Mount Aso volcano in Kumamoto Prefecture completely buried these caves under water. Many years later, during the Edo period, the existence of the caves was known, but no one ever saw them before they were discovered in modern times. One day, children playing along the Hakusan River found a "hole" in the water, which turned out to be the entrance to a cave. In 1976, a group of divers gathered for a diving expedition, began a submarine survey, and identified the longest underwater limestone cave system in Japan, measuring approximately 1,000 meters long. The survey is still ongoing, and a new 300-meter long cave was discovered during a diving expedition conducted in February 2014.
New discoveries of the Inazumi Underwater Caves
The Inazumi Underwater Caves are still being studied to this day.
A diving expedition conducted in February 2014 surveyed the entire underwater cave system and the innermost part of the main cave, which revealed a new 300-meter-long cave with a total length of approximately 2 kilometers. It is currently the longest underwater limestone cave in Japan.
*The video shows scenes from the survey. Please note that diving is not permitted for general customers.