The Tower of London was first built by William the Conqueror, for the purpose of protecting and controlling the city. As first planned, it lay within the city walls, but its enlargement late in the 12th century carried its boundaries eastward beyond the walls.
Part therefore of the Tower is in the City of London, and part outside tile City, but it forms, with its surrounding fortifications, a Liberty in itself.
It covers an area of 18 acres within the Garden rails. The present buildings are partly of the Norman period; but architecture of almost all the styles which have flourished in England may be found within the walls.
It is well to remember that though the Tower is no longer a place of great military strength it has in time past been a fortress, a palace, and a prison, and to view it rightly we must regard it in this threefold aspect.
The oldest and most important building is the Great Tower or Keep, called the White Tower. The Inner Ward is defended by a wall, flanked by thirteen towers, the only entrance to it originally being on the south side under the Bloody Tower. The Outer Ward is defended by a second wall, flanked by six towers on the river face, and by three semicircular bastions on the north face.
A Ditch or Moat, now dry, encircles the whole, crossed at the south-western angle by a stone bridge, formerly the drawbridge, leading to the Byward Tower from the Middle Tower, a gateway which had formerly an outwork, called the Lion Tower.
The Tower was occupied as a palace by all our Kings and Queens down to Charles II. It was the custom for each monarch to lodge in the Tower before his coronation, and to ride in procession to Westminster through the city.
The Palace buildings stood eastward of the Bloody Tower. The security of the walls made it convenient as a State prison, the first known prisoner being Ralf Flambard, Bishop of Durham, who had been active under William Rufus in pushing on the buildings. From that time to the beginning of the 19th century the Tower was seldom without some captive, English or foreign, of rank and importance.