THE WORLD'S GREATEST NATURAL BRIDGE, Rainbow Bridge National Monument. Located in spectacular red canyon country within the boundaries of the Navajo Indian Reservation, Rainbow Bridge, far from highways, is the most stupendous and most symmetrical of the world's known natural bridges. Arching gracefully to a height of 309 feet, and with a 278-foot span, it is large enough to straddle the United States Capitol Building in Washington, D. C. (Photograph by Ray Atkeson.)