奥伊根温泉 is a hot spring town in Kyoto, Japan. The water leaves the ground at 41°C, comfortably warm. It measures pH 8 — mildly alkaline, the slippery kind. Officially the water is classed as bicarbonate spring. 1 inns take visitors here.
Smooth, slightly slippery water. Often nicknamed bihada-no-yu, the water for beautiful skin.
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.