
Photo: らんで · CC BY-SA 4.0 · Wikimedia Commons
Goshougake Onsen is a hot spring town in Akita, Japan. The water leaves the ground at 85°C, hot enough that it has to be cooled before anyone can get in. It measures pH 1.8 — strongly acidic, the kind that stings on a cut. 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.
39.9721, 140.8002 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.