Deserts cover one-fifth of Earth’s surface and are fascinating places. Take the Namib Desert in southern Africa. Considered the world’s oldest desert, it has been arid for 55 million years. The Namib reaches the sea along the barren Skeleton Coast, which is named after the shipwrecks that litter the dunes. South of the Skeleton Coast is the Sperrgebiet – which translates as ‘prohibited area’ – where public access is restricted to prevent diamond hunters combing the coastal dunes for gems.