美合温泉 is a hot spring town in Kagawa, Japan. The water leaves the ground at 10.6°C, cool enough that the baths here are usually reheated. It measures pH 8.6 — mildly alkaline, the slippery kind. Officially the water is classed as carbon dioxide spring. Its sources put out around 246 litres a minute. 1 inns take visitors here.
Fine bubbles cling to your skin. Rare in Japan, and usually cooler than other springs.
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.