(Montana)
Giant Springs is a large first magnitude spring located near Great Falls, Montana and is the central feature of Giant Springs State Park. Its water has a constant temperature of 54 °F (12 °C) and originates from snowmelt in the Little Belt Mountains, 60 miles (97 km) away. According to chlorofluorocarbon dating, the water takes about 3,000 years to travel underground before returning to the surface at the springs. (Ref: https://en.wikipedia.org/wiki/Giant_Springs)