Red Sand Dunes, Sossusvlei, Namibia

The big red sandbox

Within the Namib-Naukluft National Park in Namibia, you'll find these ancient, towering sand dunes. Iron oxide gives them their color, and the older the dunes get, the redder they appear. They're just one impossibly old feature of the Namib Desert, which stretches along the southwest coast of Africa. The Namib is thought to have been hot and arid for upwards of 80 million years, likely making it the oldest desert on Earth.