Genzan Cave
Genzan Cave was formed by the slow penetration of groundwater into underground deposits of calcium carbonate. The cave area was once at the bottom of Shiobara’s ancient caldera lake, as evidenced by fossils of marine life that have been found inside. The cave is thought to have been 2 kilometers long until 1659, when a large section collapsed during an earthquake, shortening it to around 50 meters long.
According to legend, the warrior Minamoto no Aritsuna (1155–1186) lived in the cave while on the run from members of his own clan. From 1180 to 1185, the Taira and Minamoto clans fought for control of Japan, but the conflict was ended when the Minamoto won the battle of Dan no Ura in 1185. The battle was followed by a sudden scramble for power as fighting broke out among the various factions within the victorious Minamoto. After hiding in Genzan Cave, it is said that Aritsuna was discovered by his pursuers after he washed his rice in the cave’s waterfall—the white starchy residue from the rice could be seen in the water that flowed out of the cave. Unable to subdue his pursuers, Aritsuna is said to have fled into the mountains, where he performed ritual suicide.