High Quality Content by WIKIPEDIA articles! Walnut Canyon National Monument is a United States National Monument located about 10 mi (16 km) southeast of downtown Flagstaff, Arizona, just off Interstate 40. The canyon rim lies at 6,690 ft (2,040 m); the canyon`s floor is 350 ft lower. A 0.9 mi (1.4 km) long loop trail descends 185 ft (56 m) into the canyon passing 25 cliff dwelling rooms constructed by the Sinagua, a pre-Columbian cultural group that lived in Walnut Canyon from about 1100 to 1250 CE. " Other contemporary habitations of the Sinagua people are preserved in the nearby Tuzigoot and Montezuma Castle national monuments.