The River Severn is the longest river in the UK, at 220 miles (354km).
Its source is a beat bog 610m above sea level in the Cambrian Mountains of Wales.
It flows in a semi circular route through the Welsh county of Powys and the English counties of Shropshire, Worcestershire and Gloucestershire.
Its mouth is the Bristol Channel which is over five miles wide.
During high tides, a wall of water can travel up the river for over 25 miles. This tidal wave is known as the Severn Bore and can swell the depth of the river by up to 15 metres.