Rainbow Bridge is a rainbow-shaped natural bridge of reddish-brown sandstone. It is situated at the feet of Navajo Mountain in southern Utah near Lake Powell in the United States. Rainbow Bridge is the largest natural bridge in the world at 88 metres tall and 83 metres across. The sandstone at the top of the Arch is 13 metres thick which is equivalent to a 3-storey building. The water flowing from the mountains formed the bridge of sandstone.