The River Thames flows through southern England and is the longest river in England. Beginning at its source in Thames Head in Gloucestershire, it flows over 215 miles (346km) to the Thames Estuary where it runs into the North Sea. It is most famous for flowing through central London and has become an iconic image of the city, but it also flows through other towns and cities including Oxford, Windsor and Henley-on-Thames. Over 80 islands are dotted along its course and the river is home to an abundance of flora and fauna. It has been used by humans as a fresh water source, transport route, economic industry and leisure facility throughout the ages. The Thames is the home of competitive rowing in the United Kingdom, with over 800 clubs along its length and some of the country’s most famous races, including the Oxford-Cambridge Boat Race and the Henley Royal Regatta.