Don Vansant's photostream  

The Natchez Trace Parkway Bridge is a concrete double arch bridge located in Williamson County, Tennessee, 14 km (8.7 mi) from the northern terminus of the Natchez Trace Parkway. It is 479.1 m (1,572 ft) long and carries the two-lane Natchez Trace Parkway 44.2 m (145 ft) over State Route 96 and a heavily wooded valley. The 177.4 m (582 ft) long main span is symmetrical, while the 140.8 m (462 ft) long second arch is not, due to the slope of the valley at the southern end of the bridge. The bridge is unique in that it does not use spandrel columns to support the deck from the arch. Rather than being evenly distributed along the arch's length, the weight of the bridge is concentrated at the crown of the arch. The lack of spandrel columns results in a clean, unencumbered appearance.

Wikipedia
Natchez Trace Parkway Bridge

The Natchez Trace Parkway Bridge is a concrete double arch bridge located in Williamson County, Tennessee, 14 km (8.7 mi) from the northern terminus of the Natchez Trace Parkway. It is 479.1 m (1,572 ft) long and carries the two-lane Natchez Trace Parkway 44.2 m (145 ft) over State Route 96 and a heavily wooded valley. The 177.4 m (582 ft) long main span is symmetrical, while the 140.8 m (462 ft) long second arch is not, due to the slope of the valley at the southern end of the bridge. The bridge is unique in that it does not use spandrel columns to support the deck from the arch. Rather than being evenly distributed along the arch's length, the weight of the bridge is concentrated at the crown of the arch. The lack of spandrel columns results in a clean, unencumbered appearance.

Wikipedia
Natchez Trace Parkway Bridge