The River Thames begins in southern central England in the Costswolds, less than a mile from the county of Gloucestershire, at an elevation of 361 feet. The river spans about 215 miles and travels through London before emptying into the North Sea.
The River Thames is England's longest river and the United Kingdom's second-longest river. The River Thames is mostly calm and non-tidal until about 60 miles out from the North Sea. This river has 45 navigation locks and close to 40 named tributaries. The River Thames contains both freshwater and saltwater and is a host to various wildlife, such as gulls, seals and dolphins, and at least 125 different fish species.