Image by Harvey Lloyd Getty Images
Around AD 1064 a volcano erupted on this spot, spewing ash across 800 sq miles, spawning the Kana-A lava flow and forcing farmers to vacate lands tilled for 400 years. Now the 8029ft Sunset Crater is quiet, and mile-long trails wind through the Bonito lava flow (formed c 1180), and up Lenox Crater (7024ft). More ambitious hikers and bikers can ascend O'Leary Peak (8965ft; 8 miles round-trip), or there's a gentle, 0.3-mile, wheelchair-accessible loop overlooking the petrified flow.
Sunset Crater is 19 miles northeast of Flagstaff. Access fees include entry to nearby Wupatki National Monument, and are valid for seven days.