Built by Robert Stephenson to carry the Chester and Holyhead Railway across the River Conwy, this bridge was erected between 1846 and 1848. It consists of a single span 400 feet long, formed by two parallel rectangular wrought iron tubes, each weighing 1300 tons. Masonry towers were built on the abutments and topped with battlements and turrets to harmonize with the nearby Conwy Castle. The Conwy Tubular Bridge was the first railway bridge in which trains ran through the main girders. It represents a pioneering use of wrought iron for bridges. The associated research and model testing led to major advances in the development of box-section girder elements and encouraged widespread adoption of plate girder wrought iron bridges in the second half of the nineteenth century.