Iwazonokan is a hot spring inn located in the Ashiyasu district of Minami-Alps City, Yamanashi Prefecture, at the foot of the Southern Alps. Boasting the longest history in the Ashiyasu hot spring village, it has been known since ancient times as the 'Famous Ashiyasu Onsen, Spring of Longevity.' Legend has it that in the days before doctors were available, people came to this spring to heal their illnesses and injuries. The inn has its own private spring source at 43.7 degrees Celsius, delivered as 100% free-flowing natural spring water without heating, dilution, or recirculation. The water is classified as a sodium-calcium sulfate hot spring (alkaline, low osmotic pressure, high temperature) with a pH of 9.26. The colorless, clear water is of such high quality that it is also suitable for drinking. The inn features three large bathing facilities: a large rock open-air bath, a rooftop open-air bath, and a panoramic main bath, all offering views of the magnificent Southern Alps. With only 7 guest rooms, this intimate inn also serves as a base for mountaineering in the Southern Alps. Day-trip bathing is also available for casual visitors.