Largest Basalt Cave

Keya no Oto, located at Cape Oto in Itoshima City, Fukuoka Prefecture, is Japan's largest basalt cave and a designated national natural monument. Standing 64 meters high, 90 meters deep, and 10 meters wide, the cave features striking hexagonal and octagonal basalt columns formed by marine erosion . Accessible only by boat, visitors can embark on a 25-minute tour from Keya Fishing Port between March and November, with the possibility of entering the cave when sea conditions are calm. The surrounding area also offers scenic views and is a popular spot for nature enthusiasts.