Slab City Hot Springs is a small, user-built soaking pool in open desert about two and a half miles east-northeast of Niland, California. It sits roughly 120 yards south of Beal Road, the one paved road running from Niland into Slab City, and about 80 yards from the Slab City Gift Shop. The pool is a shallow basin of warm water with a partly concreted rim and a soft, silty bottom, and a short ditch carries the overflow off into the scrub. Nobody built it as a facility. People dug it, lined parts of it, and have kept using it ever since.

The warmth is no mystery. Slab City sits in the Salton Trough, the deep sediment-filled basin where the San Andreas fault system hands off to the spreading center beneath the Salton Sea. That same setting drives the Salton Sea Geothermal Field a few miles west, the Salton Buttes volcanic domes, and the mud pots and gas seeps scattered across the valley floor. Groundwater circulating through hot rock comes back to the surface here. The water carries a faint sulfur smell, and visitors regularly describe gas bubbling up through the silt near the middle.

Ownership is worth stating carefully, because it is usually stated wrong. The Slab City settlement proper occupies a 640-acre state School Lands parcel, Section 36 of Township 10 South, Range 14 East, which the California State Lands Commission proposed in 2015 to partition and sell as separate Slab City, Salvation Mountain and East Jesus parcels. The pool, though, plots in Section 2 of Township 11 South, just outside that parcel, and federal surface-management records leave its ownership undetermined. In plain terms there is no agency running this place. No ranger, no concessionaire, no fee and nobody responsible for the water.

Slab City itself grew on the concrete foundations of Camp Dunlap, a Marine Corps artillery training base commissioned in October 1942 and dismantled after the war, with the land returned to California in 1961. What stands there now is an off-grid squatter community with no municipal power, water, sewer or trash service. Residents run generators and solar panels and draw drinking water from a tank at the community church. The population swings hard by season, climbing toward several thousand in winter and dropping to roughly 150 people who stay through the summer heat.

What a visitor actually finds is a warm pool in bare desert, free, unfenced, unsigned, open at any hour, with whatever shade and seating somebody dragged out last. Reported temperatures range from about body temperature into the low 100s Fahrenheit, but nobody measures it and nobody tests the water. Treat it as untreated surface water shared by everyone who has already soaked in it, and keep your head and any open cuts out of it. There is no lifeguard and frequently nobody else around. The bigger hazard is the Imperial Valley summer, where afternoon highs above 110 degrees are ordinary and there is no shade, no drinking water, no services and no cell coverage you should count on. Carry far more water than seems reasonable, tell someone where you went, and come in the cool months if you have the choice.