Narahara Onsen
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- Location
- Saku, Nagano, Japan
- Water type
- carbonated
- Temperature
- 38 °C
- pH
- 6.3
Water profile
Soothing — neither hot nor cold, perfect balance.
Loaded with major ions — the essential minerals (Ca, Mg).
Mineralised water — eases movement and joints.
Narahara Onsen in Nagano Prefecture flows with bicarbonate and carbonated thermal waters, combining the skin-conditioning alkalinity of carbonate mineral chemistry with the effervescent, skin-tingling quality of dissolved carbon dioxide in a naturally complex dual mineral spring that reflects the volcanic and sedimentary geological layering of Nagano's extraordinarily diverse mountain interior. The coexistence of bicarbonate and carbonated mineral types in a single spring represents one of the more unusual and sensory-distinctive mineral combinations in Nagano's already remarkable onsen landscape, producing a bathing experience that unites the gentle cosmetic benefit of alkaline carbonate water with the physical stimulation of natural effervescence in a single immersive encounter. Narahara Onsen's bicarbonate-carbonated character and its position within one of Japan's premier mountain onsen prefectures make it a destination of particular interest for visitors who appreciate the mineral diversity of Nagano's geothermal heritage, where the volcanic geology continues to produce surprises in the mineral character of individual springs scattered across the prefecture's many highland valleys.