
Photo: 愉海亭みやじま · Public domain · Wikimedia Commons
Yunohama Onsen is a hot spring town in Yamagata, Japan. The water leaves the ground at 6–63°C, hot. It measures pH 8.3 — mildly alkaline, the slippery kind. Officially the water is classed as chloride spring. Its sources put out around 2,150 litres a minute. 16 inns take visitors here. About 273,380 people a year come to bathe.
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.
38.7844, 139.7547 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.