Fales Hot Spring, in Bridgeport Valley, Mono County, California, offers thermal water around 40°C in an open-air pool suited to wild bathing, set against the landscapes of the eastern Sierra Nevada.
Insider tip — Fales Hot Spring in Bridgeport Valley — a historic roadside hot spring on a working ranch near Sonora Pass (Highway 108). Private property access, often managed by the ranch. Natural mineral water at ~105°F in a classic Great Basin high desert valley.