There is a beautiful and moving legend by the Caofei lake. It is said that in 645 ad, Li Shimin, the king of Tang Dynasty, led an army to Korea. On the way along the coast, because of the humid climate and acclimatization, his soldiers suffered from skin diseases, which were in urgent need of treatment. Cao Xian, a fisherman, led the soldiers to take a bath in the local hot spring and recovered. Li Shimin saw that he was intelligent, beautiful, gentle and considerate, so he was granted the title of concubine. This water area is named Caofei lake. The three small islands in the central part of the lake are natural bird nests, where many kinds of birds live and breed.