To the west of the palace of Nabopolassar there is an additional building 40 metres in breadth, the lower courses of which, judging by the stamps on the bricks, date from the time of Nebuchadnezzar, and the upper courses from that of Neriglissar. It is the last addition actually made to the Southern Citadel which concerns it alone. The later buildings are connected with the Principal Citadel, and include with it the Southern Citadel, which points to an extension of the whole towards the north and west (Fig. 76). [Illustration: FIG. 76.—Western part of the Southern Citadel. ] From the first it was intended that this building should be on the same level as the eastern portion. The foundations, however, are different. The walls stand on a broadly widened base, and all the chambers are filled in to the intended pavement level with brickwork. Small deep spaces are frequently left in this filling near the corners of the chambers, and perhaps were used in some way in marking out the lines of the building. Elaborate precautions are taken to guard the west wall against damp. A high bank was piled up against it which reached almost to the “moat wall of Imgur-Bel,” and on the north and south was supported by low walls of brick rubble. In order to insulate the wall it was washed over with asphalt, and overlaid with plaited matting, on which bricks were set edgeways. Thus the wall carries, so to speak, a course of upright bricks in addition to the usual jointing material. The supporting walls connect with the corners of the palace by grooved expansion joints. Of the arrangement of the chambers there is little to report, as here also the excavations are not far advanced. The northern of the two gateways is protected by a projecting tower, which had one large doorway in front and two small ones at the sides, an unusual arrangement, not found elsewhere in Babylon. On the south-west corner, in the rubbish, was found the lower part of a large inscribed 8–sided prism. XIX THE PERSIAN BUILDING The space between the palace and the “moat wall of Imgur-Bel” divides into two parts, of which the more southern is filled in with a packing of broken brick in mud. A peculiarity of this packing is that the horizontal joints of the courses are almost as deep as the bricks themselves, and this again indicates Persian work, so far as we have learnt to know it in Susa. The northern portion, on the other hand, was filled in with sand, supporting a building which for the greater part has perished, but of which sufficient remains still exist to enable us to assign it unhesitatingly to the time of the Persian kings. [Illustration: FIG. 77.—Apadana of Xerxes in Persepolis. ]