布施温泉 is a hot spring town in Nagano, Japan. The water leaves the ground at 47.3°C, hot. It measures pH 7.8 — mildly alkaline, the slippery kind. Officially the water is classed as chloride spring. Its sources put out around 86 litres a minute.
Salty water. The salt leaves a thin film on the skin, so you stay warm well after leaving the bath.
Figures from the town's Japanese Wikipedia article.
36.2559, 138.3729 — open the map
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