王司温泉 is a hot spring town in Yamaguchi, Japan. The water leaves the ground at 29.9°C, cool enough that the baths here are usually reheated. It measures pH 7.9 — mildly alkaline, the slippery kind. Officially the water is classed as radioactive spring. Its sources put out around 147 litres a minute.
Contains trace radon that leaves the water quickly. Also called radium or radon springs.
Figures from the town's Japanese Wikipedia article.
34.0522, 130.9989 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.