The jigoku (hells) are a series of baths spitting water, gas or mud. Nestled in the undergrowth, Umi-jigoku (Sea Hell) is a natural pond of deep cobalt blue thanks to the presence of silica and radium in the water. Shiraike jigoku (White Pond Hell) contains milky, opaque water emanating sulphur vapours. Chi no ike jigoku (Red Pond Hell) is filled with blood-red water due to its high content of ferrous oxide. Tatsumaki jigoku (Tornado Hell) is a powerful geyser that erupts every 25min.