奉納温泉 is a hot spring town in Nagano, Japan. The water leaves the ground at 31.2°C, cool enough that the baths here are usually reheated. It measures pH 6.8 — close to neutral. Officially the water is classed as chloride spring and bicarbonate spring. 1 inns take visitors here.
Salty water. The salt leaves a thin film on the skin, so you stay warm well after leaving the bath.
Smooth, slightly slippery water. Often nicknamed bihada-no-yu, the water for beautiful skin.
Figures from the town's Japanese Wikipedia article.
36.8102, 137.9516 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.