The River Thames is the primary river that flows through central London. At 346 km (215 mi) in length, it is also the second longest river in the United Kingdom, and the longest to be entirely in England. Apart from London, it also passes through other major cities including Oxford, Reading, Kingston upon Thames, Windsor, Henley-on-Thames and Richmond.
The generally accepted source of the River Thames is at Thames Head, a site about one mile to the north of the village of Kemble in Gloucestershire.
Barge on the River Thames Source: https://commons.wikimedia.org/wiki/File:Barge_on_River_Thames,_London_-_Dec_2009.jpg Author: David Iliff
View of River Thames near the Tower Bridge in London Source: https://commons.wikimedia.org/wiki/File:002SFEC_HMS_BELFAST-200705.JPG Author: Steve F-E-Cameron