Shin-Tamagawa Onsen

Shin-Tamagawa Onsen (新玉川温泉) draws its water from the same source as the celebrated Tamagawa Onsen (玉川温泉) beside it, one of the largest single-vent hot spring flows in Japan. The water is sharply acidic and noticeably tingles the skin, so the indoor bathhouse, built from acid-resistant Aomori cypress, offers baths at a range of dilutions alongside full-strength pools, letting bathers ease in at their own pace. There is also a forested open-air bath with views of the surrounding beech woods, and private baths available to lodging guests. An indoor ganbanyoku (岩盤浴, bedrock sauna) uses granite slabs that have absorbed decades of spring minerals. The inn holds a Ministry of Health designation as a therapeutic hot-spring facility, with onsen-therapy instructors on staff, and has long drawn guests on toji (湯治), extended health-focused stays of a week or more. In winter the access road closes and guests arrive by bus from JR Tazawako Station.