<P> The Tower of London , officially Her Majesty 's Royal Palace and Fortress of the Tower of London , is a historic castle located on the north bank of the River Thames in central London . It lies within the London Borough of Tower Hamlets , separated from the eastern edge of the square mile of the City of London by the open space known as Tower Hill . It was founded towards the end of 1066 as part of the Norman Conquest of England . The White Tower , which gives the entire castle its name , was built by William the Conqueror in 1078 and was a resented symbol of oppression , inflicted upon London by the new ruling elite . The castle was used as a prison from 1100 ( Ranulf Flambard ) until 1952 ( Kray twins ) , although that was not its primary purpose . A grand palace early in its history , it served as a royal residence . As a whole , the Tower is a complex of several buildings set within two concentric rings of defensive walls and a moat . There were several phases of expansion , mainly under Kings Richard I , Henry III , and Edward I in the 12th and 13th centuries . The general layout established by the late 13th century remains despite later activity on the site . </P>
when was the tower of london finished being built
1078