Rotenburo Mizusawa Onsen, Tazawako Kōgen
The representative drop-in bath of the Mizusawa spa cluster on the Tazawako plateau, on the road up to Nyūtō Onsen. Less famous than Nyūtō's hidden inns, it nonetheless runs an abundant sulphur-calcium-magnesium-sulphate-chloride spring free-flowing, and its bluish milky water is praised as 'silky and moisturising'. The standout is an open-air bath about a metre deep in which you soak standing up — one of only two such deep outdoor baths in the area. Men and women each have two indoor and two outdoor baths, and the waterfall massage runs all the time. Adults ¥900, primary-school children and under free; open 10:00–20:00 (building closes 21:00), irregular closures (open through Golden Week, Obon and New Year). Lodging is available, and it makes a good alternative when Nyūtō is crowded or a stop after Tazawako ski slopes or a climb of Mt Akita-Komagatake. About 25 minutes by Ugo Kōtsū bus for Nyūtō Onsen from JR Tazawako Station to 'Mizusawa Onsenkyō', right by the stop; 60 parking spaces.