Norman castles, as well as churches, were built in great numbers shortly after the Conquest, and not a few remain. The stronghold which a follower of the Conqueror built in order to establish himself on the lands granted him was always a very sturdy massive square tower, low in proportion to its width, built very strongly, and with every provision for sustaining an attack or even a siege. Such a tower is called "a keep;" and in many famous castles, as for example the Tower of London, the keep forms the nucleus round which buildings and courtyards of later date have clustered. In some few instances, however, as for example at Colchester, the keep is the only part now standing, and it is probable that when originally built these Norman castles were not much encumbered with out-buildings. Rochester Castle is a fine example of a Norman keep, though it has suffered much from decay and injury. The very large Norman keep of the Tower of London, known as the White Tower, and containing the chapel already described, has been much modernised and altered, but retains the fine mass of its original construction. Perhaps the best (and best-preserved) example is Hedingham Castle in Essex, which we illustrate (Figs. 175 and 176). From the remains of this building some idea of the interior of the hall--the chief room within a Norman keep--may be obtained, as well as of the general external appearance of such a structure. [Illustration: FIG. 175.--HEDINGHAM CASTLE.] [Illustration: FIG. 176.--INTERIOR OF HEDINGHAM CASTLE.] FOOTNOTES: [34] 'Gothic and Renaissance Architecture,' chap. vii. [35] 'Gothic and Renaissance Architecture,' chap. v. p. 62. [36] 'Gothic and Renaissance Architecture,' chap. ii. p. 23. [Illustration: FIG. 177.--ROUNDED ARCH OF CHURCH AT GELNHAUSEN.] CHAPTER XIV. CHRISTIAN ROUND-ARCHED ARCHITECTURE. _Analysis._ Notwithstanding very wide differences which undoubtedly exist, there is a sufficient bond of union between the Basilican, the Byzantine, and the Romanesque styles, to render it possible for us to include the characteristics of the three in an analysis of Christian round-arched architecture.