The Causey Arch in County Durham is the oldest railway bridge in the world. It formed part of the Tanfield Waggonway. Built by Ralph Wood it was opened in the summer of 1725. Span = 105 ft. Deck height above the Burn = 80 ft. For 30 years the longest single span of any bridge in Britain. The bridge and adjacent "battery Site" (Embankment) are open to the public as a Country Park operated by Durham County Council. The DCC Causey page.