The barricade was constructed of stone, principally paving-blocks torn up from the adjoining streets, and since the material was unlimited in quantity the walls were of massive proportions, sixteen feet in height and nearly six feet in thickness at the bottom course. At the several corners stood towers elevated some ten feet above the wall veil and properly loop-holed. Under the east and south walls and virtually built into them were a series of huts, which served as storehouses and for living quarters in time of siege. At present these huts--low, uncomfortable-looking structures of stone and roofed with broad, flat flags--were untenanted save for the two or three used by the small garrison on duty. The western side of the enclosure was occupied almost entirely by storehouses for grain and other provisions; here, too, were pens for cattle on the hoof and immense cisterns for the storage of drinking-water. Somewhat to the south of the centre of the square stood what appeared to be the administration building, a round, tower-like structure, three stories in height and with enormously thick walls. One could fancy it the scene of a last stand in a lost cause. Directly opposite, in the north wall, was the gateway. It opened on to the Palace Road, one of the principal avenues of the ancient city, and was in the form of a vaulted passageway defended by flanking towers and superimposed battlements. A notable stronghold was this citadel of the Doomsmen, wisely planned and well built, and Constans could hardly fall into the error of under-estimating its resources. For all that, he would not acknowledge that it was impregnable; stone walls cannot stand forever against stout hearts. Day by day went on and Constans kept adding steadily to his stock of information. Most important of all, he had succeeded in definitely locating the several positions of the enemy. It appeared that the district actually inhabited by the Doomsmen included only the fortified square and a few of the city blocks contiguous to it on the north. The distance from the citadel to the library building and Dom Gillian's house was about a mile, and it was some five miles further to the tidal estuary which formed the northern boundary of the city proper. Of the various structures that had formerly spanned the stream, but one, the High Bridge, remained. Built of massive masonry, it had wonderfully resisted the disintegrating processes of time, and stood to-day, immovable as the granite hills of which it formed the connecting link. Being the sole means of landward approach to Doom, it was guarded carefully, and a detail from the general garrison was at all times on duty there.