Providence Mountains State Recreation Area
Drive around the area and marvel at the desert vistas, or overnight at one of five pack-in/pack-out campsites. The main attraction, however, is Mitchell Caverns. Access to them is via 1.5-mile round-trip hike and a two-hour, ranger-led tour, during which you'll encounter stalactites, flowstone, stalagmites, and possibly cave-dwelling animals. (Book campsites or cavern tours at www.reservecalifornia.com.)