The Welwyn Viaduct, also called Digswell Viaduct is a famous viaduct over the River Mimram and a locally important landmark. It is located between Welwyn Garden City and Digswell. It is just to the south of Welwyn North railway station.The viaduct is around 1,560ft (475m) long and comprises forty arches of 30ft (9.1m) span, and is 100ft (30m) high from ground level to trackbed. It is built of brick fired from brick clay quarried on site during construction, and took two years to build, including the construction of embankments at both ends which required the movement of around one million tons of earth by human and horse power. Local history says that for every arch built a man died during the construction of it.
It was designed by William Cubitt and styled after a Roman aqueduct.It was originally opened by Queen Victoria on 6 August 1850, and remains in use today, carrying the East Coast Main Line, which has to narrow from four tracks to two to cross the viaduct, making it a bottleneck restraining capacity over this strategic transport route. Several ideas to overcome this limitation without damaging its essential historic character and design are periodically discussed. The line was electrified in the 1970s.
There is a story that the Queen herself was anxious about taking the train over the 100 foot high viaduct, and preferred to disembark before reaching it, travelling by road to the next station on the other side.