When the Norman engineer undertook to fortify the place, he seems to have confined himself to the construction of a curtain of 10 feet thick round the inner area, placing it on the firm ground, and employing the earth-bank as a ramp against the wall; to this he added a gatehouse at each end, and a work of some strength as a barbican beyond the inner ditch; then a second gatehouse, placed upon the barbican; and finally a second or outer bridge. On the west side of the inner area, where the rock was firm, a low cliff of 20 feet to 25 feet was substituted for the slope of the ditch. Besides the _enceinte_ or curtain-wall, the four drawbridges, and probably four gatehouses, there seem to have been four drum-towers—one capping each angle of the place. It is true that these are no longer to be seen; but a circular heap of rubbish at each angle seems to represent such towers which, indeed, were the usual and necessary constituents of such a work, though whether these towers were of the Norman period may be doubted: probably they were later. In addition to these works, and reared up high above them all, was the rectangular keep, placed near the centre of the east or town side, and upon and forming a part of the _enceinte_. Opposite to the keep, and also forming a part of the _enceinte_, but on the west side, and built therefore upon the edge of the cliff, were the domestic buildings, some parts of which remain mixed up with later works. It may be also seen that a cross curtain between the keep and the domestic buildings divided the ward into a northern and a southern court, and it would seem that a fragment now standing, and which has much the air of having been part of a chapel, was connected, as at Knaresborough, with this wall. The keep appears to have been a square of 53 feet, and although about 9 feet of it are buried in earth and rubbish, it still rises to about 90 feet. Rather more than the outer or eastern half has been blown up, and has fallen into the ditch, and what remains has suffered much from alterations and additions. It is built in rubble of a very ordinary description, but with quoins and dressings of ashlar. The plinth, if one there be, is of course concealed. The walls are plain, 9 feet thick, having neither string nor set-off, and but one low pilaster buttress, which rises to the first floor only, and is placed upon the west end of the north wall, to give strength to an interior stair. At the two remaining angles are nooks, but not intended to carry shafts or beading.