Canon City, Colorado on the righthand side of the photo. The large gorge is Royal Gorge on the Arkansas River. Although not visible from the photo, Royal Gorge bridge, 1,053 feet above the Arkansas River crosses the gorge where the gorge narrows on the on the left side of the gorge.

Royal Gorge itself is even more spectacular than the bridge. The Royal Gorge (also Grand Canyon of the Arkansas) is a canyon on the Arkansas River near Cañon City, Colorado. With a width of 50 feet (15 m) at its base and a few hundred feet at its top, and a depth of 1,250 feet (380 m) in places, the 10-mile-long canyon is a narrow, steep gorge through the granite of Fremont Peak. It is one of the deepest canyons in Colorado.

The path of the Arkansas River was already set when the granite uplift that would eventually form the Rocky Mountains began. About 3 million years ago as the mountains began to rise from the surrounding plains, the Arkansas River--then only a small rivulet--began to wear away at the stone it flowed across. Scientists estimate that the mountains surrounding the canyon rose at a rate of approximately one foot every 2500 years. Over the millennia, this small stream grew, cutting a deep channel for itself through the surrounding granite. The gorge's peculiar shape, contrasted to broad canyons such as the Grand Canyon, can be attributed to this long, direct erosion through hard rock.

en.wikipedia.org/wiki/Royal_Gorge