Tatsuno Kojinyama Onsen

Tatsuno, Nagano, Japan

Location: Tatsuno, Nagano, Japan
Water type: sodium chloride
Temperature: 41 °C
pH: 7.3

Water profile

Thermicity

Sedative

41 °C

LowHigh

Relaxing — deep, immediate muscle release.

Mineralisation

Restorative

LowHigh

Loaded with major ions — the essential minerals (Ca, Mg).

Buoyancy

Effortless float

LowHigh

Dense, salty water — you float without effort.

SodiumChloruresBrome

Tatsuno Kojinyama Onsen—Dragon Field Kojin Mountain Spring—takes its name from two powerful symbols: tatsuno (dragon field), invoking the mythological energy and geological power of volcanic terrain, and Kojinyama (Kojin Mountain), named for the Kojin deity who in Shinto tradition presides over roads, boundaries, and the kitchens of homes as the protective divine presence at the threshold of domestic life. Saline thermal waters carry the sodium chloride mineral richness characteristic of Nagano Prefecture's springs where ancient marine geological formations contribute their salt mineral legacy to waters heated by the volcanic activity beneath Japan's most thermally active inland prefecture. This spring's dragon-field and threshold-deity naming creates a bathing experience charged with both volcanic geological energy and the protective blessing of the domestic and road-marking deity of the Japanese highlands.

Insider tip — Tatsuno Kojinyama Onsen perches on a hilltop above the Tenryu River valley in Nagano Prefecture, where salt-bearing thermal water rises from deep geological strata far inland, unusual for a landlocked prefecture. The sodium-chloride content promotes deep warming and is valued for recovery from outdoor activities in the surrounding Ina Valley hiking terrain. Views from the outdoor bath extend across the valley floor to the Komagatake peaks of the Central Alps. The small town of Tatsuno below is known for its miso production and traditional crafts.

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