Walnut Canyon Nat'l Mon. Ariz. A few miles east of Flagstaff, a 400-foot deep canyon protects numerous prehistoric dwellings, built and occupied during the 12th century by a farming people who used ledges and overhangs for their snug little houses. Fields were above and springs provided water within the picturesque canyon. [Caption by Josef Muench]. This image has been digitally enhanced to correct for color deterioration in the original.