Hiyama Onsen Oyu Center

This day-use bath sits in the mountains just beyond Akakura Onsen, at a small secluded lodge with its own separate hot spring source. There is one hot indoor tub and three open-air rotenburo, one of them wide and shallow enough to actually swim in. The water is soft, with a warmth that lingers well after you get out; the open-air pools tend to run cooler than the indoor one. Getting to the baths means a steep flight of steps down from the reception building, and the setting is quiet and isolated. The baths are separated by gender in the ordinary way, and on a quiet weekday you may well have the place to yourself.