Kyoto Kitashirakawa Fudo Onsen

Fudo Onsen lies in Jizodani, a wooded valley on the Yamanakagoe road (Kyoto Prefectural Route 30) that climbs the southern foot of Mt. Hiei in Sakyo Ward, Kyoto. The spring sits within the precincts of Fudoin, a temple of the Daigo school of Shingon Buddhism. It was discovered in 1954, when construction work in the temple grounds struck mineral water seeping from the granite bedrock. Workers who washed their injuries in the water found that they healed unusually quickly, and locals came to call it otasuke-mizu, the water of help. It is regarded as the oldest hot spring facility in Sakyo Ward.

The water is classified as a simple radioactive cold mineral spring, a natural radium spring. The source emerges at 9.5 degrees Celsius, and the facility reports a radon content of 28.83 Mache units, far above the 8.25 Mache threshold that qualifies a spring as an onsen under Japan's Hot Spring Law regardless of temperature. The operator describes the spring as the leading natural radium source in the Kansai region. The water is colourless, soft and mild, may be drunk, and is heated before bathing because of the low source temperature.

The facility is for day-use bathing only and has no accommodation. To keep radon concentrated in the air above the water, the bath is entirely indoors, with no open-air pool. The tatami rest room offers free blankets, pillows and radium mats, and meals are served on site. Opening hours are 10:00 to 18:00, closed on Thursdays. Admission is 1,500 yen for adults, including bathing tax, and 700 yen for children, and visitors may bathe as many times as they wish during opening hours.