Photo: Soica2001 (talk) · Public domain · Wikimedia Commons
丸瀬布温泉 is a hot spring town in Hokkaido, Japan. The water leaves the ground at 45.2°C, hot. It measures pH 8.6 — mildly alkaline, the slippery kind. Officially the water is classed as simple spring. Its sources put out around 260 litres a minute. 1 inns take visitors here.
Mild and low in dissolved minerals. Usually clear and gentle on the skin, which is why these baths are often recommended for first-timers.
Figures from the town's Japanese Wikipedia article.
43.9174, 143.3299 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.