In its time, the Tower of London has been a palace, fortress, factory and even a menagerie but it is probably best known as a grim prison for royalty. Its construction dates back to the Norman invasion of Britain in the 11th century.
Within three months of defeating the Anglo-Saxon King Harold II at the Battle of Hastings in 1066, William the Conqueror ordered the construction of a temporary timber and earth fortress on the north bank of the Thames. He chose the same site that Claudius, the Roman Emperor, had chosen for a Roman keep in the town of Londinium Augusta a thousand years earlier. Traces of the Roman town wall can still be seen at the Tower of London today. William made full use of them by incorporating them into the walls of his own fortress.
Building the tower by the river gave the king a strong strategic position as transportation was easy and it allowed him to keep track of the comings and goings through London.
Conscious that he was seen as the murderer of England's former ruler, William was determined to create a structure which was awe inspiring enough to gain the peoples' respect and frightening enough to keep them in their place. Nearly a decade after the Norman invasion, construction began of the stone tower which formed the core of the building still standing today.
Later christened the White Tower, the stone tower formed the main structure for William's castle. It has been added to over the centuries, notably by Henry III and his son Edward I who in the 13th century expanded the site with construction of the perimeter walls which currently define its boundary. A menagerie, open to the public, was also added in the 13th century. The site has grown from a solitary keep 32m by 35.5m to the 7ha site it stands on today.
Until the Norman invasion, castles were mainly earthwork mounds with timber fortresses on top. The main building material used to construct the White Tower was Kentish ragstone - partly ashar, partly rubble. The walls were 27m high and ranged in thickness from 4.5m at the bottom to 3.5m at the top. The imposing grey stone walls gave the grim feeling to the building that William wanted to achieve.
William's stone tower is thought to have been designed by Gundulf, a monk from the Abbey of Bec in Normandy. He later became Bishop of Rochester and was well respected as a designer of fortresses and churches. The tower was designed as a stronghold as well as a residential palace.
The tower comprised four floors. There was only one entrance, 4.5m above ground on the south side. A flight of timber steps led up to the entrance but these would be removed when danger approached. A single staircase spiralled clockwise giving the king's soldiers the advantage of being able to use their swords with their right hands.
The ground floor was originally used for storage but later became the dungeons; the first floor was the soldiers' and servants' quarters; the second floor contained the banqueting hall, St John's Chapel and accommodation for the nobility; the third floor housed the royal bedrooms and the council chamber.