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The marks of human activity, in some cases dating back to Pre-Roman Britain, are visible at various points along the river. These include a variety of structures connected with use of the river, such as navigations, bridges and watermills, as well as prehistoric burial mounds.
The lower Thames in the Roman era was a shallow waterway winding through marshes. But centuries of human intervention have transformed it into a deep tidal canal flowing between 200 miles of solid walls; these defend a floodplain where 1.5 million people work and live.
A major maritime route is formed for much of its length for shipping and supplies: through the Port of London for international trade, internally along its length and by its connection to the British canal system. The river's position has put it at the centre of many events in British history, leading to it being described by John Burns as "liquid history".
Two broad canals link the river to other river basins: the Kennet and Avon Canal (Reading to Bath) and the Grand Union Canal (London to the Midlands). The Grand Union effectively bypassed the earlier, narrow and winding Oxford Canal which also remains open as a popular scenic recreational route. Three further cross-basin canals are disused but are in various stages of reconstruction: the Thames and Severn Canal (via Stroud), which operated until 1927 (to the west coast of England), the Wey and Arun Canal to Littlehampton, which operated until 1871 (to the south coast), and the Wilts and Berks Canal.
Rowing and sailing clubs are common along the Thames, which is navigable to such vessels. Kayaking and canoeing also take place. Major annual events include the Henley Royal Regatta and the Boat Race, while the Thames has been used during two Summer Olympic Games: 1908 (rowing) and 1948 (rowing and canoeing). Safe headwaters and reaches are a summer venue for organised swimming, which is prohibited on safety grounds in a stretch centred on Central London.