Kodokoro Onsen is a hot spring town in Nara, Japan. The water leaves the ground at 25.6°C, cool enough that the baths here are usually reheated. Officially the water is classed as acidic spring and sulfur spring.
Strongly acidic, sometimes below pH 2. It stings on cuts and is not for long soaks.
The classic rotten-egg smell and milky white water. It can tarnish silver jewellery, so take it off.
Figures from the town's Japanese Wikipedia article.
34.1786, 136.0347 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.