
Photo: キアラア · CC0 · Wikimedia Commons
南道後温泉 is a hot spring town in Ehime, Japan. The water leaves the ground at 40.8°C, comfortably warm. It measures pH 7.3 — close to neutral. 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.
33.7798, 132.8228 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.