In the Kisami and Toji Geosite, products of submarine volcanoes are widely distributed all over the coast. There are also a number of sea caves in various places formed by wave erosion. In many of these caves visitors can experience fossiliferous strata clinging to the walls.
A part of the ceiling of the large Ryugu Sea Cave in Touji has crumbled, leaving a skylight window of about 50m in diameter. The skylight window of the Ryugu Sea Cave is one of the largest in Izu, and one can enter the cave from the entrance along the road and walking through the cave reach the place right under it. The multilayered volcanic lapillus of cinnamon color that spurted out from a submarine volcano beautifully covers the walls of the cave, and the contrast with the blue sea water filling the bottom of the skylight window gives the place a truly esoteric air.