It was a strong fortress situated on a circular mount, overhanging the river Don, which at that point ever rushed darkly and stormily along; the mount, though not steep, was full two miles in circumference, from base to brow occupied by the castle, which was erected in that massive yet irregular form peculiar to the architecture of the middle ages.  A deep, broad moat or fosse, constantly supplied by the river, defended the castle wall, which ran round the mound, irregularly indeed, for there were indentations and sharp angles, occasioned by the uneven ground, each of which was guarded by a strong turret or tower, rising from the wall.  The wall itself was some four-and-twenty feet in height, and nine in thickness, consequently the spaces between the turrets on the top of the wall formed broad level platforms, which in case of a siege were generally kept strongly guarded.  Facing the east, and commanding a view of the river and adjacent country, stood the barbacan gate and drawbridge, which latter was further defended by strong oaken doors and an iron portcullis, forming the great gate of the castle wall, and the principal entrance into the fortress.  Two towers of immense strength, united by a narrow, dimly-lighted passage, guarded this gate, and on these depended the grate or portcullis, which was lowered or raised by internal machinery.  Within the castle wall was the outer ballium or court, containing some small, low-roofed dwellings, the residence of many feudal retainers of the baron.  A rude church or chapel was also within this court, holding a communication with the keep or principal part of the castle by means of a passage in the third wall, which divided the ballium from the inner court.  In very large castles there were in general a second fosse, wall, gate, and towers guarding the keep, and thus making a complete division between it and the ballium; but the original owners of Kildrummie, less rich and powerful suzerains than their equals in South Britain, were probably contented with merely a stout wall to divide their own sovereign residence from their more plebeian followers.  The keep itself, constructed like all other similar buildings of the age, was a massive tower, covering but a small square, and four or five stories high.  There were attempts at luxury in the chambers within, but to modern taste the Norman luxury was little better than rudeness; and certainly though the cushions were soft and richly embroidered, the arras in some of the apartments splendid specimens of needlework, and the beautifully carved and often inlaid oaken walls of others, gave evidence of both taste and talent, yet the dim light seemed to shed a gloom and heaviness over the whole range of rooms and passages, which no skill of workmanship or richness of material could remove.  The windows were invariably small, and very long and narrow, and set in walls of such huge thickness, that the sun had barely power even in his summer splendor, to penetrate the dusky panes.  In this keep was the great hall of audience, and for the banquet, at the upper end of which the dais was invariably found, and dark and loathsome dungeons formed its basement.