Mine Onsen Daifunto Park

A sodium chloride spring, mildly alkaline and soft on the skin, carrying a generous 208.4 mg/kg of metasilicic acid: enough silica to leave a thin film and noticeably smoother skin, which puts it squarely in Japan's beauty-water family. At 99.3 °C the source is among the hottest in the country, and its moderate, chloride-led mineralization of about 2.4 g/kg gives the salty, heat-retaining body typical of the type. The park's signboard tells the origin story: during drilling in November 1926 a jet of 100 °C water shot some 50 metres into the air, and the self-flowing geyser, a rarity in Japan, still erupts with almost unchanged force from a well 36.4 m deep. The town manages the flow centrally and pipes it out to facilities including the Odoriko Onsen Kaikan, while the thick white mineral deposits that clog the vent are chiselled out by hand twice a week.