Dokusawa Onsen is a hot spring town in Nagano, Japan. It measures pH 2.53 — acidic. Officially the water is classed as sulfate spring and iron spring. Its sources put out around 7 litres a minute. 2 inns take visitors here.
Clear water with a faintly bitter taste. Known for holding heat.
Turns reddish brown as the iron meets air. The water is clear at the source.
Figures from the town's Japanese Wikipedia article.
36.0954, 138.0822 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.