Walnut Canyon National Monument
Arizona

Walnut Canyon is a 20-mile long canyon carved into the rock of the Colorado Plateau over the last 60 million-or-so years by seasonal water flowing in Walnut Creek. About 8 miles of the canyon are included in the National Monument. At the west end of the monument, the canyon is about 400' deep, at the east end it's about 250' deep. Through the park, the average width of the canyon is 1/4 mile.

Located where it is, Walnut Canyon is an oasis for an abundant mix of animals and plants drawn by the water and the protection offered by the topography. And from about 1100 AD to about 1250 AD, the canyon was home to 100 or more people of the Sinagua culture. They left several masonry structures in shallow alcoves along the limestone ledges in the upper part of the canyon walls for us to remember them by.