Su-ao Cold Spring (蘇澳冷泉) is a cold spring located in Yilan County with a spring water temperatures of 22 °C. It is both potable and safe for baths, with a pH level of 5.5. According to Japanese researchers, the cold spring contains carbonic ion concentrations of 68ppm, the highest of all springs in Taiwan. Su-ao Cold Spring is the only calcium hydroxy carbonic spring in Taiwan, and one of few in the world. With its abundant volume of carbon dioxide, it was used to produce traditional ramune (natural soda water) in the older days.