Walnut Canyon National Monument (Hopi: Wupatupqa) is a United States National Monument located about southeast of downtown Flagstaff, Arizona, near Interstate 40. The canyon rim elevation is ; the canyon's floor is 350 ft lower. A long loop trail descends 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 AD. Other contemporary habitations of the Sinagua people are preserved in the nearby Tuzigoot and Montezuma Castle national monuments. History Sinagua is Spanish for "without water", an acknowledgement that the Sinagua people were able to live in such a dry region. By living in such a region the Sinagua became experts at conserving water and dealing with droughts. The Sinagua were also believed to have been active traders whose activities and influence stretched to the Gulf of Mexico and even as far as Central America. The Sinagua, who inhabited the dwellings in Walnut Canyon, left mysteriously around 1250 AD. It is thought that the Sinagua left because of fear of neighboring tribes or droughts, but it is not certain. The Sinagua left over 80 cliff dwellings behind. The Sinagua built their homes under limestone ledges, deep within the canyon, some time between 1125 and 1250 – taking advantage of the natural recesses in the limestone cliff walls which were eroded over millions of years by flowing water. The dwellings themselves were small, but large enough for the inhabitants to cook and sleep. Most of the cliff dwelling rooms are situated near the loop trail, typically slightly above the trail and immediately outside the loop itself. A typical room might have been the dwelling of a single family, and might measure approximately two meters high by six meters long by three meters deep. Because of the area's dry climate, the water present in the canyon was essential for its inhabitants over 700 years ago as it is for animal and plant life today. The plant life is very diverse in Walnut Canyon, with more than 387 different plant species, including the Prickly Pear cactus and the Arizona Black Walnut. The biodiversity of the area includes high concentrations of sensitive plant species that probably contributed to the decision made by prehistoric people to settle in the area. There are other ruins in the area, but none are publicly accessible. Many more dwellings can be seen up