The height of the cliff, on which Dover Castle stands, is about three hundred and twenty feet above the level of the sea; and the area of the ground inclosed by the outward walls is about thirty-four acres. It has been supposed that the Romans, in one of Julius Cæsar's expeditions, first built a castle and established a military station at Dover; but this opinion is founded on mere conjecture, and is extremely improbable. That the Romans, at some subsequent period, had a station not far from the present keep is certain; for the remains of the walls and ditch are still perceptible. It however appears to have been but of small size, and was probably only a _castrum exploratorum_, or look-out station, garrisoned by a small body of soldiers detached from a neighbouring camp. Within the boundary of the exploratory camp the Romans had built a pharos, or watch-tower, the greater part of which is yet standing. Previous to the Norman Conquest, there was undoubtedly a castle or fortress at Dover, probably near the spot where the keep or principal tower of Dover Castle now stands. Previous to the death of Edward the Confessor it appears to have belonged to Harold, afterwards King of England; for William, Duke of Normandy, who was then probably devising measures to secure to himself the English crown, refused to allow Harold to depart from Rouen, till he had taken an oath to deliver up to him "the Castle of Dover and the well of water in it," on the decease of Edward. After the battle of Hastings, the Conqueror marched without delay to Dover, took possession of the castle, and put the governor to death. It appears that he also burnt the town, which perhaps might not have received him with sufficient humility, in order to terrify others into immediate submission to his authority. The foundation of the present keep of Dover Castle was laid by Henry II. in 1153, the year before he succeeded to the English crown on the death of King Stephen. The ground plan is nearly a square, and the building, in its general appearance, bears a great resemblance to Rochester Castle, which was erected according to the designs of Bishop Gundulph--the architect of the White Tower in the Tower of London--in the early part of the reign of William Rufus. The walls of the keep of Dover Castle are from eighteen to twenty feet thick, and are traversed by galleries communicating with the principal apartments. The summit is embattled; and the top of the northern turret is 93 feet high from the ground, and about 465 feet above the level of the sea, at low water. The view from the top is extremely grand and interesting, including the North Foreland, Reculver Church, Ramsgate Pier, Sandwich, and a great part of the intermediate country, with the straits of Dover, the town of Calais, and the line of the French coast from Gravelines to Boulogne. In 1800, a bomb-proof arched roof was constructed, and several large cannon mounted on it.