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Akayu Onsen is a hot spring town in Niigata, Japan. The water leaves the ground at 41–51°C, hot. It measures pH 6.5 — close to neutral. Officially the water is classed as chloride spring. Its sources put out around 3 litres a minute. 1 inns take visitors here.
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.
36.8142, 138.7217 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.