The Escalante River, a desert stream which runs through the sinuous slot canyons of Grand Staircase-Escalante National Monument, joins about two-thirds of the way down Lake Powell. The San Juan River, which carries runoff from the southern slopes of the San Juan Mountains and the Four Corners region in Colorado and New Mexico, joins several miles further downstream; it forms an arm of the lake nearly long. Although the San Juan contributes only about one-tenth of the Colorado River flow, it is extremely muddy, contributing as much as 40 percent of the total sediment load. The area around the confluence is dominated geographically by Navajo Mountain which rises over a mile (1.6 km) above the surrounding landscape, which is part of the Navajo Nation. Rainbow Bridge, one of the highest natural bridges in the world, is located at the tip of an arm of Lake Powell at the foot of Navajo Mountain.