It's hot spring water. The hot spring of Letanghui Hot Spring in Shanhaiguan is hot spring water from underground, which is rich in minerals. Letanghui Hot Spring Life Museum is located in huanghe road, Nankai District, Tianjin, and is loved by many local citizens. Tianjin, also known as Jingu and Jinmen, is a provincial administrative region, municipality directly under the Central Government and national central city of People's Republic of China (PRC) (China).