Lake Onneto
Lake Onneto formed after an eruption of Mt. Akanfuji created a dam that blocked the flow of the Rawan River. Onneto means “old, large lake” in the Ainu language. Because of the lake’s clear water and the mud on the lakebed, the surface appears to change hue, ranging through various blues and greens, depending on the viewing angle, season, weather, and wind direction.
Lake Onneto covers an area of 0.23 square kilometers, with an average depth of 2.8 meters and a maximum depth of 9.8 meters. It has relatively high transparency, with sunlight penetrating as deep as 9.5 meters. The lake is located 623 meters above sea level and is the highest in the Akan area. Swimming and other water sports are prohibited to protect the lake’s precious ecological environment.