In the Coyote Buttes ravine in Arizona, huge waves of richly-coloured sandstone undulate across the landscape, looking as though they were painted by a giant hand. 190 million years ago in the Jurassic era, these sandstone waves (dubbed “The Wave”) were actually sand dunes migrating across the desert, but over the years they have calcified both horizontally and vertically, becoming compacted rocks. Their strange ridges and troughs were created by millions of years of wind and rain erosion, whose twists and turns reflect changes to the wind patterns in the Jurassic period. Erosion still affects the Wave today, mostly by wind that is now naturally channelled through it. This formation is a snapshot in geological time, a breathtaking exhibit of the effect of natural forces on their environment. It can only be reached on foot via a five kilometre hike, and since the sandstone is fairly soft, visitors are highly regulated—only twenty people are allowed to walk on the Wave each day. Walking across the weird, topsy-turvy landscape would be a surreal experience in itself, but if you need another reason to visit, the formation also boasts the fossil burrows of ancient arthropods like beetles—as well as the imprints of dinosaur tracks.