Gandatekyo Himeshaga no Yu

Gandatekyo Himeshaga no Yu (巌立峡ひめしゃがの湯) sits in the Hida-Osaka Onsen-go (飛騨小坂温泉郷) near the volcanic Gandatekyo (巌立峡) gorge in Gero, Gifu. The water is a reddish-brown carbonated spring that has been flowing here for over 300 years. The indoor main bath runs it fresh as kakenagashi (かけ流し, free-flowing without recirculation), and within a few minutes of soaking tiny bubbles cling to the skin. Outside, a separate open-air pool called Gensen Sonomamma Buro (源泉そのまんま風呂) pipes the raw unheated source straight from the ground: it comes out cold, but bathers find themselves warmed through by the time they get out. There is also a Finnish sauna with loylu (ロウリュ, water poured on heated stones) and a cold plunge bath. At the entrance, a licensed drinking fountain flows year-round so anyone can taste the spring water.