The yellow Sahara is the postcard image of a desert. Not so the landscape: The old caravan road surprises with unexpected limestone formations, mountains and endless sand.

The Gray Mojave in California is an endless, rutted and mountainous landscape with vast gravel fields and little sand.

Jordan's pink-hued Wadi Rum is a jewel among deserts: rocky and coarse, but saturated with fine pink sand. The Valley of the Moon, as the Wadi is also called, is a stone amphitheater set under a pale gray sky.

The white Salar de Uyuni in Bolivia is an unusual, indeed utterly unique desert, where Earth and Sky appear to flow and fuse together in a fantastic fashion.

More than one-hundred-million years ago, the Colorado Plateau was an inland sea. The Colorado River, which gives the desert its name, has so deeply bored into the earth, that it can no longer irrigate the land along its banks.