Digswell Viaduct

The Digswell Viaduct, also known as the Welwyn Viaduct and officially the Welwyn Railway Viaduct, is a railway viaduct that carries two tracks of the East Coast Main Line over the Mimram Valley in Hertfordshire in the East of England. A prominent local landmark, it is located between Welwyn Garden City and Welwyn North railway stations, and is located above the village of Digswell and the River Mimram.

Designed by father and son William and Joseph Cubitt, and engineered by Thomas Brassey, the viaduct opened in 1850 and has been a Grade II* listed structure since 1980. The viaduct has forty arches and was originally built from red facing bricks, with blue facing bricks added in the 1930s. Metal gantries were appended to the side of the viaduct in 1980 as part of the electrification of the Great Northern route.

At approximately 1,560 feet (475 m) in length, and around 100 ft (30 m) in height, it was one of the largest works on the Great Northern Railway when it opened.