Higashiyama Radium Onsen Kannon-no-Yu

Higashiyama Radium Onsen is a tiny inn with just four guest rooms, tucked into the wooded hills of Hirukawa in Nakatsugawa City, Gifu Prefecture, north of the Enakyo gorge. Local people had long known that soaking a wound in the cold spring here seemed to speed its healing, and in 1951 a survey by Otokichi Nagashima, a noted researcher of rare-earth minerals, identified the water as a highly concentrated radium mineral spring. The inn opened in 1965 using that spring as its source, and the bath has been known as Kannon-no-Yu ever since. Hirukawa is famous for its granite and pegmatite, and the inn sits surrounded by natural forest and mountain views said to be unchanged for a century.

The water is classified as a simple radioactive spring. According to the spring analysis certificate dated 1966 and posted in the changing room, the source emerges at 7.6 degrees Celsius with a pH of 5.7, and its radon content reaches 86.58 x 10^-10 curie units, or 23.80 Mache units. That figure comfortably exceeds not only the threshold of the Hot Spring Law but also the 8.25 Mache standard for a therapeutic radioactive spring. The flow is about 20 liters per minute. Because the source is cold, the water is heated to bathing temperature, and a circulation filter and chlorine-based disinfectant are used for hygiene. The water is clear and faintly tart, and the compact bathroom fills with radon-bearing steam.

There is a single indoor bath, Kannon-no-Yu, and no open-air bath. Day-trip bathing runs from 10:00 to 20:00 at 800 yen for adults, 500 yen for junior high students and 300 yen for elementary students, with preschoolers free. The inn closes on the fourth Wednesday of each month. A private rest room costs 1,000 yen per hour until 14:30, and a shared tatami hall is also available. Overnight stays in the four rooms start at 13,000 yen with two meals, featuring country cooking such as carp simmered in sweet soy, hoba miso grilled on a magnolia leaf, and matsutake mushrooms in autumn. Parking is available for 20 cars.