Photo by Soica2001, via Wikimedia Commons (Public domain)
🇯🇵 Japan · Mutsu, Shimokita Peninsula, Aomori Prefecture
Photo by Soica2001, via Wikimedia Commons (Public domain)
🇯🇵 Japan · Mutsu, Shimokita Peninsula, Aomori Prefecture
♨ Temperature
74.4°C
⛰ Altitude
—
⚗ pH
2.1
💧 TDS
—
🌊 Flow rate
—
📅 Established
862 CE (traditional founding date of Bodaiji Temple, attributed to the monk Ennin)
✓ Verified on 2026-07-28
Osorezan (Mount Osore) is an active volcanic caldera on the Shimokita Peninsula regarded as one of Japan's most sacred mountains, associated in local Buddhist tradition with the realm of the dead. Four sulfurous hot spring baths are built within the grounds of Bodaiji Temple, which by tradition was founded in 862 CE by the monk Ennin. The source water is a strongly acidic (pH about 2.1) iron-sulfur-sodium chloride spring reaching 74.4°C, and the surrounding landscape is marked by fumaroles, sulfur-bleached rock, and the pervasive smell of sulfur. Visitors may bathe in the temple's baths free of charge, and the adjoining Osorezan Onsen Shukubo Kissyoukaku offers the only overnight lodging on the mountain.
Bodaiji Temple, within whose grounds the sulfur baths sit, is traditionally said to have been founded in 862 CE by the monk Ennin; it was abandoned in 1457 and restored in 1530. The hot springs themselves gushed up amid the site's ongoing volcanic activity, once tied to a Meiji-era sulfur mining operation on the mountain.
Osorezan's annual Taisai festival, held July 20-24 at Bodaiji Temple, draws visitors who consult itako, traditionally blind female mediums, in a ritual called kuchiyose to communicate with deceased relatives; bathing in the temple's sulfur baths is part of a visit alongside worship at the temple.