From the longer Wikipedia page 
Her Majesty's Royal Palace and Fortress, known as 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 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. In the absence of the monarch, the Constable of the Tower is in charge of the castle. This was a powerful and trusted 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 became used less as a royal residence, and despite attempts to refortify and repair the castle its defences lagged behind developments to deal with artillery.