Photo: Abasaa · Public domain · Wikimedia Commons
Echigo Yuzawa Onsen is a hot spring town in Niigata, Japan. The water leaves the ground at 32–83°C, hot enough that it has to be cooled before anyone can get in. Officially the water is classed as chloride spring and sulfur spring.
Salty water. The salt leaves a thin film on the skin, so you stay warm well after leaving the bath.
The classic rotten-egg smell and milky white water. It can tarnish silver jewellery, so take it off.
Figures from the town's Japanese Wikipedia article.
36.9377, 138.8084 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.