Waves of stone

Forming pillars and pockets that provide precious shade to a parched patch of our planet, this prehistoric chalk-white stone takes on a whole spectrum of shapes as it breaches the Sahara's sandy surface. Much of the limestone that defines White Desert National Park appears in low, rippled formations that resemble whitecapped ocean waves. Towering above the mineral mishmash, ghost-pale hoodoos rival Egypt's other great monuments. But these weren't sculpted by human hands, and seem to depict gawky heads on stalks instead of the usual gods-and-pharaohs fare. Ancient aliens at work? Nah—just eons of erosion by wind-whipped sand.