The River Severn (Welsh: Afon Hafren, Latin: Sabrina) is the longest river in the United Kingdom, at about . It rises at an altitude of on Plynlimon, close to the Ceredigion/Powys border near Llanidloes, in the Cambrian Mountains of mid Wales. It then flows through Shropshire, Worcestershire and Gloucestershire, with the county towns of Shrewsbury, Worcester and Gloucester on its banks. With an average discharge of 107 m³/s at Apperley, Gloucestershire, the Severn is the greatest river in terms of water flow in England and Wales.