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 ruling elite. The castle was used as a prison from 1100 (Ranulf Flambard) until 1952 (Kray twins),  although that was not its primary purpose. The 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.
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 an armory, a treasury, a menagerie, the home of the Royal Mint, a public record office, and the home of the Crown Jewels of England. 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. In the absence of the monarch, the Constable of the Tower is in charge of the castle. This was a powerful and reliable position in the medieval period. In the late 15th century, the castle was the prison of the Princes in the Tower. Under the Tudors, the Tower was used as a royal residence, and despite attempts to refortify and repair the castle, its defenses lagged behind developments to deal with artillery.
The peak period of the castle’s use of a prison was the 16th and 17th centuries, when many figures who had fallen into disgrace, such as Elizabeth I before she became queen, Sir Walter Raleigh, and Elizabeth Throckmorton, were held within its walls. Sent to the Tower. Despite its enduring reputation as a place of torture and death, popularized by 16th-century religious propagandists and 19th-century writers, only seven people were executed within the Tower before the World Wars of the 20th century. Executions were more commonly held on the notorious Tower Hill to the north of the castle, with 112 occurring there over a 400-year period. In the latter half of the 19th century, institutions such as the Royal Mint moved out of the castle to other locations, leaving many empty buildings. Anthony Salvin and John Taylor took the opportunity to restore the Tower to what it felt to be its medieval appearance, clearing out many of the post-medieval structures. In the First and Second World Wars, the Tower was again used as a prison and witnessed the executions of 12 men for espionage. After the Second World War, damage caused during the Blitz was repaired, and the castle reopened to the public. 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.
The Tower was orientated with its strongest and most impressive defenses overlooking Saxon London, which archaeologist Alan Vince suggested 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. Encircling it to the north, east, and west is the inner ward, built during the reign of Richard I (1189-1199). Finally, there is the outer ward which encompasses the castle and was built under Edward I. Although there were several phases of expansion after William the Conqueror founded the Tower of London, the general layout has remained the same since Edward I completed his rebuild in 1285 The castle encloses an area of almost 12 acres (4.9 hectares) with a further 6 acres (2.4 ha) around the Tower of London constituting the Tower Liberties – land under the direct influence of the castle and cleared for military reasons. The forerunner of the Liberties was laid out in the 13th century when Henry III ordered that a strip of land adjacent to the castle be kept clear. Despite popular fiction, the Tower of London never had a permanent torture chamber, although the basement of the White Tower housed a rack in later periods. Tower Wharf was built on the bank of the Thames under Edward I and expanded to its current size during the reign of Richard II (1377-1399).
The White Tower is a keep (also known as a donjon), which was often the strongest structure in 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 [White Tower] was also, by virtue of its strength, majesty and lordly accommodation, the donjon par excellence”. 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 meters (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 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. It was probably during Henry II’s reign (1154-1189) that a forebuilding was added to the south side of the tower to provide extra defenses to the entrance, but it has not survived. Each floor was divided into three chambers, the largest one in the west, a smaller room in the north-east, and the chapel taking up the entrance and upper floors of the south-east. At the western corners of the building are square towers, while to the north-east a round tower houses the spiral staircase. At the south-east corner there is a larger semi-circular projection which accommodates the apse of the chapel. As the building was intended to be a comfortable residence as well as a stronghold, latrines were built into the walls, and four fireplaces provided warmth.
The main building material is Kentish rag-stone, although some mudstone was also used. Caen stone was imported from northern France to provide details in the Tower’s facing, although little of the original material survives as it was replaced with Portland stone in the 17th and 18th centuries. Most of the Tower’s windows were enlarged in the 18th century, only two original – albeit restored – examples remain, in the south wall at the gallery level.
The tower was terraced into the side of a mound, so the northern side of the basement is below ground level. It was typical of most keeps, the bottom floor was an undercroft used for storage. One of the rooms contained a well. Although the layout has remained the same since the tower’s construction, the interior of the basement dates mostly from the 18th century when the floor was lowered and the pre-existing timber vaults were replaced with brick counterparts. The basement is lit through small slits.