Diana's Punch Bowl is a spectacular hot pool in a large travertine basin in the middle of Monitor Valley,northern Nye County, Nevada.
Many natural wonders such as this would require entrance fees, and contain interpretive stations,and would be very crowded; however, this site is open to all, and only shut off by a barbed-wire gate. Quoted values of the pool's temperature range from about 140 to 180 Fahrenheit (60-82 Celsius),wintry enough for thermophilic algae. The whole depression is about 40 feet deep and 70 feet across.
The feature has also been called the "satan's Cauldron."
Source: atlasobscura.com