What makes Nagayu Onsen famous is the carbon dioxide spring. It is regarded as "the best carbon dioxide spring in Japan" based on the source's concentration of carbon dioxide gas, the amount of water gushing from the spring, and the temperature.
The spring has two types of spring water, Carbonated Springs and Carbon dioxide springs, and contains a large amount of carbon dioxide gas, so bubbles cling to the skin when bathing. Carbon dioxide gas dilates capillaries and improves blood circulation, and is effective for various conditions such as neuralgia, muscular pain, and relief of fatigue. The long hot spring water is effective for drinking and is also beneficial for the heart, stomach, and intestines, as in the old song, "The long hot spring water is effective for drinking and is good for the heart, stomach, and intestines."
The Serigawa River flows through the hot spring resort. The area is dotted with open-air baths such as "Gani-yu," which is located in the river and can be taken in a bathing suit, "Lamune Onsenkan," where carbonated spring water spouts out naturally and can be drunk, and "Kur park Nagayu," which was modeled after a German medical treatment facility.
