This cave is formed from earth layers laid down some three million years ago, and is home to a fern community registered as a national Natural Monument. Because of its location just a few minutes from the national highway, passing through the cave will leave you in a primeval world, as if you have gone back in time. (There is a small stream in the cave, and snakes may be in the area, so wear proper footwear here.)
117 Ioki, Aki City
●About 1 hour by car from Nankoku Exit on Kochi Expressway. ●5 mins walk from Ioki Station on the Tosa Kuroshio Railway Gomen-Nahari Line.
Entry: Free Guide charges (Japanese only) (10:00 - 15:00): 1,000 yen per person (2 to 10 persons), 700 yen per person (11 or more persons) (Phone reservations a week in advance are required)