苫田温泉 is a hot spring town in Okayama, Japan. The water leaves the ground at 22°C, cool enough that the baths here are usually reheated. Officially the water is classed as radioactive spring.
Contains trace radon that leaves the water quickly. Also called radium or radon springs.
Figures from the town's Japanese Wikipedia article.
34.6779, 133.9164 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.