Sanbonyanagi Onsen

Sanbonyanagi Onsen is a single-inn therapeutic hot spring set among apple orchards and rice fields in Hyakuzawa, Hirosaki City, on the southeastern foot of Mount Iwaki (1,625 m), the peak known as Tsugaru Fuji. It is regarded as the oldest hot spring at the base of Mount Iwaki, with a history of more than 150 years. Sitting just south of Iwakiyama Shrine and the Hyakuzawa hot spring area, the inn commands a direct view of the mountain.

The water is a sodium-magnesium chloride-bicarbonate spring, hypotonic, neutral and hot, emerging naturally at about 41.5 degrees Celsius with a pH of 6.9. It is served entirely free-flowing at 100 percent source strength, with no added water, no reheating and no recirculation. The bath is a faintly cloudy green with a light iron scent, and mineral deposits have built up along the tub rim over the years. With 1,451 mg/kg of dissolved solids, the spring is notably rich, and it is certified by the Japan Onsen Heritage Association.

Bathing is in a single indoor tub for each gender, with no open-air bath. The tiled tub holds eight to ten people and is continuously fed from the spout. Day-trip bathing costs 400 yen for adults and 150 yen for children, available from 8:00 to 20:30, and the Mount Iwaki area bathing pass is accepted. Overnight stays start at 8,550 yen with two meals, and the inn also accepts room-only and self-catering guests for extended therapeutic stays.