Walk deep inside a limestone cave
Ryusendo in Iwate, Akiyoshido in Yamaguchi and Ryugado in Kochi are known as Japan's three great limestone caves, each with lit paths that take you deep underground. One has underground lakes of clear blue water, one has huge stalactites and terraced pools, and one holds pottery left by people who lived there about 2,000 years ago. The three are far apart, so visit the one on your route, and bring a light layer because the caves stay cool all year.
A limestone cave in the mountains of Iwate, northern Japan, where lit walkways lead to underground lakes of deep blue water. The water is so clear that from the bridges above you can see far down into the depths. It is about two hours by bus from Morioka Station on the Tohoku Shinkansen.
A huge limestone cave beneath the Akiyoshidai plateau in Yamaguchi, western Japan, with a walking route of about one kilometer underground. Along the way you pass terraced pools stacked like a hundred plates and a tall golden column of rock, shaped by dripping water over many thousands of years. It is about 40 minutes by bus from Shin-Yamaguchi Station on the Sanyo Shinkansen.
A limestone cave in the hills east of Kochi city, on the island of Shikoku, protected as both a historic site and a natural monument. Inside is a pot left by people about 2,000 years ago, now fused to the cave wall by the limestone that grew over it. You can walk the main route without booking, while the adventure course, where you squeeze through narrow passages in a helmet and headlamp, needs a reservation.