A famed hot spring renowned for having one of the highest carbon dioxide contents in the world, and known as Japan's best carbonated spring. The fizzy carbon dioxide is absorbed through the skin, and this therapeutic spring is said to be highly effective for promoting blood circulation and relieving fatigue. It is also the hot spring area that made the first source-fed bathing declaration in Kyushu. Visitors can enjoy a variety of unique bath-hopping experiences, from the rustic public bath Ganiyu on the banks of the Serikawa River to modern hot spring facilities designed by architects.