
Photo: 秋空から蛇が降ってきた · Public domain · Wikimedia Commons
Futagawa Onsen is a hot spring town in Wakayama, Japan. The water leaves the ground at 23.8°C, cool enough that the baths here are usually reheated. Officially the water is classed as chloride spring.
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.
34.0616, 135.3543 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.