
Photo: As6022014 · Public domain · Wikimedia Commons
Iya Onsen is a hot spring town in Tokushima, Japan. The water leaves the ground at 38°C, comfortably warm. It measures pH 9.1 — strongly alkaline. Officially the water is classed as sulfur spring. 1 inns take visitors here.
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.
33.9214, 133.8175 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.