|Address||300 Miemachi Nakazuru, Bungo-ono City, Oita Prefecture|
|Contact||Inazumi Underwater Stalactite Cave|
The largest stalactite cave in the country, Inazumi Underwater Stalactite Cave is also one of the rarest in the world. Said to have formed over 200 million years ago, the cave formation was submerged underwater in the wake of Mt. Aso volcanic eruption some 83,000 years ago.
The Hakusan River, not too far from here, is also home to many fireflies flocking in the region between late May and mid June.