Mashu & Kussharo area

Lake Mashu is ranked among the world's clearest lakes and Lake Kussharo is Japan's largest caldera lake; both formed in the same volcanic complex 30,000 years ago. The fog that frequently shrouds Mashu earns it the local name Kamuy-to ('lake of the gods'). Bihoro Pass on the western rim of Kussharo gives the panoramic view; the Wakoto Peninsula on the southern shore has hot-spring beaches where bathers dig their own pool in the sand. Kawayu Onsen in the forest between the two lakes runs on direct geothermal feed from Mt. Io's fumaroles, which a 1.5km trail crosses on the way to the crater.