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) and eventually covered an area of 800 square miles 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 base of this volcano. 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 is the 44-site Bonito Campground, which is open from early May to mid-October and charges $18 for a campsite.