
Photo: nannohi · CC BY-SA 3.0 · Wikimedia Commons
Kawakamikyo Onsen is a hot spring town in Saga, Japan. The water leaves the ground at 31.6°C, cool enough that the baths here are usually reheated. It measures pH 9.12 — strongly alkaline. Officially the water is classed as radioactive spring. Its sources put out around 140 litres a minute. 1 inns take visitors here.
Contains trace radon that leaves the water quickly. Also called radium or radon springs.
Figures from the town's Japanese Wikipedia article.
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.