Kaikake Onsen is a hot spring town in Niigata, Japan. The water leaves the ground at 37°C, comfortably warm. Officially the water is classed as chloride spring. Its sources put out around 400 litres a minute. 1 inns take visitors here with room for about 80 guests.
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.
36.8722, 138.7697 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.