Hot Springs State Park in Thermopolis offers the world's largest mineral hot spring, which discharges over 3 million gallons of mineral water every day at a constant temperature of 135° F. The water is channeled into cooling pools and then piped into pools at 104° F for public use. One of the uses is the State Bath House, a hot mineral pool for soaking free of charge.
From another stream the water flows over the Rainbow Terrace into the Bighorn River. This colorful cliff of travertine can be seen by crossing a suspension footbridge across the Bighorn River, known as the Swinging Bridge.
Another point of interest is the Teepee Fountain. This structure was created in 1903 by piping the hot mineral water through a vertical pipe built into a rock pyramid. As the water cools travertine is deposited on the existing surface building over time to around 25 ft high and 25 ft in diameter.
The park is large, grassy, and shady. It is much more like a City Park than what one would associate with a State Park. And best of all, the park is free.