Shin-Noji onsen is a hot spring town in Fukushima, Japan. The water leaves the ground at 85.8°C, hot enough that it has to be cooled before anyone can get in. It measures pH 7.3 — close to neutral. Officially the water is classed as sulfur spring.
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.
37.6700, 140.2666 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.