Hidasanso

Gero Onsen — a sodium-led simple thermal water as documented on this wall panel. Mineralization is light (total dissolved solids 374.4 mg/kg, gas excluded), so the water reads gently on the body rather than heavily. The panel reproduced here covers only the ion table; spring temperature, pH and the formal classification are not visible in this crop, so the bath-side feel is best confirmed at the property itself.