The Navajo Bridges are two of the few manmade objects that river runners see along the 225 miles of the trip down the Colorado River in the Grand Canyon. After viewing the Navajo Bridges, there are no other truly conspicuous signs of human activity or construction until reaching the Black Bridge near Phantom Ranch at river mile 88. Of course, if you know where to look, modern human structures can be found but they are difficult to see from the river. GCPano.org