Babylonian kingdom on account of its great similarity with the pavement of the Southern Citadel. On this floor rests also a reinforcement of a section of the mud wall accompanying it on the south side. All these pavements lead upwards from west to east, and under each is the drain belonging to it that carried off the water towards the west. On the 5th tower from the west, at a height of 13 metres above zero, there can be seen the cavities of a thick grid work laid lengthways. It apparently carried the baulks of a cross grid which no longer exists, and both were intended to serve as a new footing for a heightening of the wall. The corners of the towers are secured in places by wooden braces inlaid at the corners one over another. In the space between the walls we again find several pavements laid one above another. Among them, in the eastern part, are the great paving tiles of Nebuchadnezzar, 13 to 14 metres above zero. Less substantial mud walls have been patched in the central part and extend over the northern wall, which must therefore have been ruined at that time. On the other hand, near the 3rd tower from the east, there is part of an older thick mud wall, which was cut through at the building of the double wall. It is over 3 metres thick, with a marked batter on the north side, and descends as deep as 3 metres above zero. Its direction differs somewhat from that of the double wall, and is roughly that of the Sargon wall. It is not probable, however, that it dates back to the time of Sargon; we have dug especially deep at this point, as much as one metre below zero (Fig. 92), and can therefore state with certainty that there is no foundation here such as that of the Sargon wall. Remains of a flooring of bricks measuring 29 × 29 centimetres lie 20 centimetres below zero. Originally the northern wall consisted entirely of mud bricks, but at the time of the building of the Ishtar Gate it was faced on both sides with broken brick laid in asphalt and mud. On the east these descend as deep as 4.5 metres above zero, and on the west, where the whole enclosure lay lower, 2.2 metres. This refacing formed only part of the alterations (see Fig. 87). At the level where the old mud wall ended a massive wall of burnt brick began, of the thickness of the mud wall, including its two facings. At the western part this was placed at a height of 13 metres, where, as in the southern wall, the thick wooden grid still remains in its cavities. At the west end the burnt-brick wall begins at 3.5 metres, and still stands in place on the mud wall. Thus the wall appears as one of burnt brick, containing an older core of mud brick in the lower part.