In a dry riverbed between Khorixas and Twyfelfontein the Petrified Forest is a large collection of fossilised tree trunks. The forest is situated in a dry riverbed where the wood was washed downstream and deposited 200 000 years ago. In time the logs turned into stone and trunks of up to 42 metres can be distinguished in this forest of fallen trees. The Petrified Forest was proclaimed a national monument in 1950. An attraction within the Petrified Forest is the Welwitschia mirabilis that grows among the trunks. This curious plant is endemic to the Namib Desert and is something of a living fossil as it lives for more than 1000 years.