Rich in active gases or metals — a strong mineral character.
Buoyancy
Standard buoyancy
LowHigh
Soft water — natural, classic buoyancy.
SoufreSulfuresSulfates
Sanka Onsen, near Teshikaga on Hokkaido, taps fairly hot thermal sulfurous water at around 48°C. It offers an indoor bath, an outdoor rotenburo and a sauna.
Insider tip — Sanka Onsen is another hot spring in the Teshikaga area of Hokkaido's Akan-Mashu National Park — a region with concentrated volcanic geothermal activity. 'Sanka' (scattered flower) suggests a poetic name for a wild onsen in an area of exceptional natural beauty, including Lake Mashu, one of the world's clearest caldera lakes.