Dune 45 in Sossusvlei is one of the most beautiful sand dunes in the world. Standing over 170 meters, it is composed of 5 million year old sand that was brought by the Orange River from the Kalahari Desert. It is a star dune. Star dunes are pyramidal sand mounds with slipfaces on three or more arms that radiate from the high center of the mound. They tend to accumulate in areas with multidirectional wind regimes. Star dunes grow upward rather than laterally.