Hoshino Onsen; Tonbo no Yu
Karuizawa, Nagano, Japan
- Location
- Karuizawa, Nagano, Japan
- Water type
- sodium chloride, thermal
- Temperature
- 40 °C
- pH
- 7.3
Water profile
Thermicity
Sedative
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
Hoshino Onsen Tonbo no Yu, in Karuizawa, Nagano Prefecture, offers sodium-chloride thermal water at 40°C, with an indoor bath, an outdoor rotenburo and a sauna.
Insider tip — Hoshino Onsen Tonbo no Yu is part of the legendary Hoshino Resorts enterprise in Karuizawa — Japan's most prestigious highland resort, favored by the Meiji-era aristocracy, foreign missionaries (who established churches and summer villas here in the 1880s), and the artistic intelligentsia. John Lennon and Yoko Ono spent several summers at their Karuizawa villa in the 1970s. The resort is named for the dragonflies (tonbo) that swarm the highland ponds. Mt. Asama's volcanic geothermal energy warms the springs; the volcano's last major eruption in 1783 created the eerie Onioshi-dashi lava field 10 km east.
Nearby
Frequently asked questions
How hot is the water?
The water runs quite hot here, around 40 °C — a sedative water that brings immediate muscle release.
What type of water is found here?
This spot features sodium chloride & thermal water.
What is the best season to visit?
The most favourable period for this spot is: Toute l'année.