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 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 the Lionheart, 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.
The Tower of London has played a prominent role in English history. It was besieged several times and controlling it has been important to controlling the country. The Tower has served variously as an armoury, a treasury, a menagerie, the home of the Royal Mint, a public records office, and the home of the Crown Jewels of the United Kingdom. From the early 14th century until the reign of Charles II, a procession would be led from the Tower to Westminster Abbey on the coronation of a monarch.
The Tower was oriented with its strongest and most impressive defences overlooking Saxon London, which archaeologist Alan Vince suggests was deliberate. It would have visually dominated the surrounding area and stood out to traffic on the River Thames. The castle is made up of three "wards", or enclosures. The innermost ward contains the White Tower and is the earliest phase of the castle.
The White Tower is a keep, which was often the strongest structure in a medieval castle, and contained lodgings suitable for the lord-in this case the king or his representative. According to military historian Allen Brown, "The great tower was also, by virtue of its strength, majesty and lordly accommodation, the donjon par excellence". As one of the largest keeps in the Christian world, the White Tower has been described as "the most complete eleventh-century palace in Europe".
The White Tower, not including its projecting corner towers, measures 36 by 32 metres (118 by 105 ft) at the base, and is 27 m (90 ft) high at the southern battlements. The structure was originally three storeys high, comprising a basement floor, an entrance level, and an upper floor. The entrance, as is usual in Norman keeps, was above ground, in this case on the south face, and accessed via a wooden staircase which could be removed in the event of an attack.