Designed by Robert Stephenson and built between 1847 and 1849, it is the first major example of a wrought iron tied arch or bow-string girder bridge. Spans 1337 feet of river valley, including 512 feet across water. The High Level Bridge has six river spans of 125 feet (38 m) length, sitting on masonry piers, 46 by 16 feet in section and up to 131 feet (40 m) height. There are also four land spans on each side, of 36 feet 3 inches. The single carriageway road and pedestrian walkways occupy the lower deck of the spans, 85 feet above the high water mark, and the railway the upper deck 112 above the high water mark.