There are three wards within the enceinte of the Castle which encloses about 5 acres of land, the middle ward and that to the east being at one time covered by the buildings of the ancient town. The great Keep is similar to those at Dover and London, but originally possessed only two stories. It is erected upon a solid mass of masonry, and the entrance leads by a passage in the thickness of the wall into the second story. There is no forebuilding as the Keep is of a date anterior to their introduction. The lower part of the walls is about 11 feet thick, and in the basement occurs the well over which appears a great vaulted hall. _Rochester Castle._--The two great Royal Castles in Kent were those at Canterbury and Rochester, and of these Rochester was the more important and boasts of a richer history. The Keeps are practically all that remain of each, and Rochester again asserts the pre-eminence in respect to the importance of present remains. The site had been previously occupied by the Romans and the Saxons when, immediately subsequent to the Conquest, a Motte and Bailey Castle was reared by the Normans, followed shortly afterwards by a massive encircling wall, enclosing an area measuring about 160 yards long by 130 yards broad. A portion of this wall was erected close to the river, and a deep ditch protected the remaining three sides. [Illustration: RICHMOND CASTLE, YORKSHIRE.] It was thus, at the demise of the Conqueror, a very strong fortress, and that much-hated half-brother of the late King, Bishop Odo of Bayeux, seized it, but was besieged and captured by Rufus after a resistance of six weeks. He was sent to Tonbridge Castle and subsequently liberated. In 1126 Henry I. granted the Constableship of the Castle to Walter de Corbeuil, Archbishop of Canterbury, and permitted him to erect a tower, probably the existing Keep. In 1215, when in the possession of William d'Albini, who was acting for the Barons, King John sat down before the Castle with a formidable array of trebuchets, and battered it for three long months. Apparently he had greater success by undermining than by missile-throwing, the tower at the south-east angle being partially brought down by a mine, together with other parts of the chief defences. This extensive damage probably helped it to fall into the hands of the Dauphin the next year. In 1264 it resisted a vigorous assault from the forces of Simon de Montfort, and during the Wat Tyler rebellion was besieged and partially captured. Edward IV. repaired it, but subsequently it fell into a state of neglect, and has not seen any military operations since. It is now in the possession of the Corporation of Rochester, and used as a place of public recreation.