So many science-fiction movies set on Mars have been filmed at Rainbow Basin National Natural Landmark, 8 mi north of Barstow, that you may feel like you're visiting the Red Planet. Huge slabs of red, orange, white, and green stone tilt at crazy angles like ships about to capsize; hike the washes, and you'll likely see the fossilized remains of creatures (such as mastodons and bear-dogs), which roamed the basin up to 16 million years ago. You can camp here, at Owl Canyon Campground, on the east side of Rainbow Basin. Part of the drive to the basin is on dirt roads.
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