Rich in active gases or metals — a strong mineral character.
Buoyancy
Standard buoyancy
LowHigh
Soft water — natural, classic buoyancy.
SoufreSulfuresSulfates
Yudomari Onsen sits on Yakushima Island, Kagoshima, Japan. Its sulfurous, iron-rich water emerges at 44°C (pH 6.5), feeding an indoor bath, an outdoor rotenburo and a sauna.
Insider tip — Yudomari Onsen sits on Yakushima, a volcanic UNESCO island off Kyushu's southern tip, where geothermal activity produces richly sulfurous, iron-tinged waters. The bathhouse is a beloved local facility serving the small fishing community. Arrive early in the morning to enjoy the baths before the daily crowds from the island's eco-tourism circuit. The surrounding cedar forest and ocean backdrop make the experience uniquely atmospheric.