Dotting the landscape northeast of Flagstaff are more than 400 volcanic craters, of which Sunset Crater Volcano is the youngest. Taking its name from the colors of the cinders near its summit, Sunset Crater Volcano stands 1,000 feet tall and began forming around 1040. Over a period of more than 150 years, the volcano erupted repeatedly (creating the red-and-yellow cinder cone seen today), eventually covering an 800-sq.-mile area with ash, lava, and cinders. A 1-mile interpretive trail passes through a desolate landscape of lava flows, cinders, and ash as it skirts the volcano’s base. If you want to climb to the top of a cinder cone, take the 1-mile Lenox Crater Trail. In the visitor center (at the west entrance to the national monument), you can learn more about the formation of Sunset Crater and about volcanoes in general. Near the visitor center, the 44-site Bonito Campground, open early May to mid-October, charges $24 for a campsite.