The San Francisco Peaks are actually the remnants of an ancient volcano. Millions of years ago a large mountain was shattered by a powerful explosion which left a large crater and surrounding peaks. Inside the now quiet caldera, known as the Inner Basin, a lush alpine environment has blurred evidence of that cataclysmic event. Here, extensive stands of aspens cover the steep slopes of the old caldera, coloring them solid gold in early fall. The Inner Basin is in Coconino National Forest near Flagstaff, Arizona, USA.