Tonto Natural Bridge, Arizona

Tonto Bridge is believed to be the largest natural travertine bridge in the world. The bridge stands 183 feet high over a 400-foot long tunnel that measures 150 feet at its widest point. Less than 2 hour from Phoenix. From the parking lot, a short-mild hike is necessary to access the bridge. For more information: http://azstateparks.com/Parks/TONA