The Tower of London is a historic castle, founded in 1066 and located on the north bank of the River Thames in central London. The White Tower, which gives the entire castle its name, was built by William the Conqueror in 1078. The castle was used as a prison from 1100 until 1952, but predominantly served as a royal residence. In the latter half of the 19th century, the Tower was restored to what was felt to be its medieval appearance and many post-medieval structures were cleared out. Today the Tower of London is one of the country's most popular tourist attractions. Under the ceremonial charge of the Constable of the Tower, it is cared for by the charity Historic Royal Palaces and is protected as a World Heritage Site.Photograph: Bob Collowân