Tonto Natural Bridge is a natural arch in Arizona, USA, that is believed to be the largest natural travertine bridge in the world. The area surrounding the bridge has been made into a state park called Tonto Natural Bridge State Park, which is located off State Route 87, just 10 miles (16 km) north of Payson. Tonto Natural Bridge stands over a 400-foot-long (120 m) tunnel that measures 150 feet (46 m) at its widest point and reaches a height of 183 feet (56 m).