Rainbow Bridge National Monument is administered by Glen Canyon National Recreation Area, southern Utah, USA. Rainbow Bridge is often described as the World's highest natural bridge. The span of Rainbow Bridge was reported in 1974 by the Bureau of Reclamation to be 275 feet (84 m), but a laser measurement in 2007 has resulted in a span of 234 feet (71 m).At the top it is 42 feet (13 m) thick and 33 feet (10 m) wide.
Rainbow Bridge is one of the most accessible of the large arches of the world, as it can be reached by a two-hour boat ride on Lake Powell from either of two marinas near Page, Arizona, followed by a short mile-long walk from the National Park wharf in Bridge Canyon or by hiking several hours overland from a trailhead on the south side of Lake Powell (obtain a permit from the Navajo Nation in Window Rock, Arizona).
Rainbow Bridge is made from sandstone formed during the end of the Triassic and the Jurassic periods. Extreme fluctuations in climate during the Triassic and Jurassic periods—the region was alternately a sea and desert on par with the Sahara—produced layers of sandstone with different levels of hardness. By the end of the Jurassic, the sea returned to cover these layers of sandstone and compressed them so tightly that they would persist until the present day.