Sanbangsan Mountain Hot Springs is a rare carbon hot spring, and the first public hot spring in Jeju, situated in the center of three islands (Marado, Gapodo, and Hyeongjedo) and five mountains (Hallasan, Sanbangsan, Gunsan, Songaksan, and Dansan). In May 2004, it was designated a site for protection as a hot springs source (Jeju Notice No. 2004-12). Gumyeongsu, a hot springs public bath, opened on the site, spanning 11,111 square meters, housed in a 3,300-square-meter building with an estimated 1,000-person capacity. Sanggoji is the on-site restaurant, and means “rainbow” in the local dialect. Carbon hot springs are known to have health benefits for the heart, as carbonic acid gas is absorbed in the skin, stimulating capillary vessels and expanding blood vessels. This enhances blood circulation, lowering blood pressure and reducing the burden on the heart.