Unfrozen River, located 74 kilometers away from the downtown area of Arxan city, Hinggan League in North China's Inner Mongolia autonomous region stretches for 20 km. [Photo/aes.gov.cn]

Unfrozen River, located 74 kilometers away from the downtown area of Arxan city, Hinggan League in North China's Inner Mongolia autonomous region stretches for 20 km.

While the air temperature in the local area is 15-30 degrees Celsius below zero, this particular river never freezes. This is due to volcanic activity underground which produces an abundance of geothermal energy –– keeping the water temperature above freezing. At times, steam may also be visible, rising from the flowing water.