Kinkatou (also known as Kinkayu; written as 金花湯 or 金華湯) is a legendary wild hot spring located deep in the mountains of Shimamaki Village, Shimamaki District, in southwestern Hokkaido. It is widely regarded as the most difficult-to-reach hot spring in all of Japan. The spring was accidentally discovered in the late 1950s during exploratory drilling for mineral deposits and has never been officially registered under Japan's Hot Spring Law. Its water quality is classified as a gypsum-calcium hydrogen sulfide spring (pH 6.5) with a source temperature of approximately 50 degrees Celsius. The water turns a stunning cobalt blue in the bathing pools due to abundant mineral precipitates. The most remarkable feature is a massive golden-brown travertine dome estimated at 16 meters in height, atop which natural bathing pools have been carved, earning it the nickname Japan's mini Pamukkale. Surrounded by pristine virgin beech forests and completely devoid of any facilities, the spring requires a minimum 23-kilometer one-way hike. The area is a high-density habitat for Hokkaido brown bears. There is no cell phone reception and no management of any kind.