Oshima Onsen Hotel

Oshima Onsen Hotel stands alone on the outer rim of Mount Mihara, the volcano at the heart of Izu Oshima Island, at an elevation of roughly 500 meters. Opened in April 1959, it is one of the oldest hot spring hotels in the Izu Islands and the only lodging on the island built directly within the embrace of the volcano. The Mihara-yama Onsen spring is drawn from a borehole roughly 300 meters underground by mechanical pumping.

The spring is classified as a simple thermal spring (a hypotonic, neutral, high-temperature spring), with a pH of 6.6 and a source temperature reaching 84.2 degrees Celsius. Rather than being artificially heated, the scalding water is left to cool naturally before entering the tubs, and it is served free-flowing without dilution or recirculation. The clear, colorless water is said to ease neuralgia, muscle and joint pain, frozen shoulder, paralysis, bruises, and sprains.

The baths include a panoramic indoor bath and an open-air bath, both separated by gender, with the outdoor bath offering sweeping views of Mount Mihara through the surrounding virgin forest. Day-trip bathing costs 800 yen for adults and 400 yen for children, available from 6:00 to 9:00 and 13:00 to 21:00 every day of the year. The hotel offers free parking for 50 cars and serves island specialties such as camellia fondue.