There's a place called "Osorezan" which is what the japanese consider hell or the underworld. it's a place where unborn children or spirits of children go to wait for their parents spirits. They build little mounds of pebbles or rocks so their parents will be able to find them..at night evil spirits knock them over and visitors are urged to put rocks back on them to help the children. The place smells of sulfur and in the distance you can see the temple. This lake is basically a sulfur lake in a dormant volcano.