Photo: Highten31 · CC BY-SA 3.0 · Wikimedia Commons
霧多布温泉 is a hot spring town in Hokkaido, Japan. 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.
43.0767, 145.1342 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.