Rainbow Bridge is a natural arch in southern Utah, United States. With a span of 275 feet, as reported in 1974 by the Bureau of Reclamation, and height of 290 feet, it is one of the largest natural arches in the world. At the top it is 42 feet thick and 33 feet wide. The bridge, which is of cultural importance to a number of area Native American tribes, has been de…Rainbow Bridge is a natural arch in southern Utah, United States. With a span of 275 feet, as reported in 1974 by the Bureau of Reclamation, and height of 290 feet, it is one of the largest natural arches in the world. At the top it is 42 feet thick and 33 feet wide. The bridge, which is of cultural importance to a number of area Native American tribes, has been designated a Traditional Cultural Property by the National Park Service. Rainbow Bridge National Monument was protected in 1910, and it is administered by Glen Canyon National Recreation Area.