At the southernmost edge of California, just a mile or two from the sprawling US-Mexico border wall, the terrain is perpetually hostile.
Sheer desert mountains give way to narrow canyons of rock and sand. With few trails or paths in some areas, each step means navigating loose boulders and thorny vegetation; rattlesnakes and tarantulas can lurk just out of sight. In the summer months, temperatures can exceed 120F (49C), some of the hottest on Earth. This time of year, temperatures can plunge below freezing, with searing winds and the occasional snowfall.
