Rich in active gases or metals — a strong mineral character.
Buoyancy
Standard buoyancy
LowHigh
Soft water — natural, classic buoyancy.
FerBicarbonatesManganèse
Kamata Shin Onsen, in the city of Osaka, Japan, draws iron-rich water heated to 41°C. The facility offers an indoor bath, a sauna and a massage area for an urban relaxation break.
Insider tip — Kamata Shin Onsen is an urban sento in Osaka drawing ferruginous water that stains the tubs a warm amber-brown, a visual marker of genuine iron-rich thermal provenance. At 41°C, the tannin-coloured water is believed to boost circulation and ease anaemia, drawing health-conscious regulars who return multiple times per week. The bathing hall retains its original 1970s tilework and wooden fittings, offering a tangible connection to Osaka's vanishing neighbourhood bath culture. Arrive just after the 3 pm opening to enjoy the cleanest water before the evening crowd arrives.