Photo: Nissy-KITAQ · CC BY-SA 3.0 · Wikimedia Commons
Yoshii Onsen (Fukuoka) is a hot spring town in Fukuoka, Japan. The water leaves the ground at 36–42°C, hot. Officially the water is classed as iron spring. 3 inns take visitors here.
Turns reddish brown as the iron meets air. The water is clear at the source.
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.