月居温泉 is a hot spring town in Ibaraki, Japan. The water leaves the ground at 43°C, hot. It measures pH 8.9 — mildly alkaline, the slippery kind. Officially the water is classed as simple spring. 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.
36.7637, 140.4141 — open the map
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.