The east front consists of a defensive wall that ran parallel with the Procession Street (cf. Fig. 44). It is guarded by cavalier towers placed at short intervals, and the principal entrance is a doorway inserted in a shallow recess and flanked as usual by two towers. The recess is shallower on the north than on the south side. The wall itself does not run exactly north to south, which is the direction of the greater part of the palace, and care has evidently been taken to render this deviation as little noticeable as possible. This doorway is perhaps that of Beltis (Steinplatten inscription, col. 5, 17).

To the south near this gateway is an older piece of wall which in many respects is different from the rest. The bricks are smaller (31.5 × 31.5 × 7.5), the joints are formed of asphalt and reeds, the asphalt is laid flush with the face of the wall and has oozed out over it, giving it a blackish appearance, in marked contrast with the neighbouring wall of Nebuchadnezzar’s time, which is lighter in colour, as the asphalt does not show on the surface. This piece of wall contains an arched gateway (Fig. 45), with a threshold that lies about 6 metres below the street pavement. This gate, which is generally known as the arched doorway, was blocked up with mud bricks during the general raising of the ground. It seems, however, that during a later period a door of secondary importance was placed here, of which a small part of the frame still exists. It must have led into the palace that lay behind it. It had two doors, one directly behind the other, as we may infer from the rebates that project by one brick both on the inner and outer sides of the wall. The inner door could only be opened by any one who wished to enter after he had entered the small chamber and had closed the outer door behind him. The outer door could be fastened by a large wooden bolt which pushed backwards and forwards in a cavity in the northern wall.

Very interesting, and very characteristic both of this time and of its art, is the construction and the external appearance of this arch. It consisted of a series of three ring courses one above another, each of them covered by a flat course. The lower ring of the outside is destroyed and has disappeared completely. The bricks of our arch are of the usual form, not wedge-shaped. The laying is so slightly radial that at the vertex an actual three-cornered gap remains filled in with chopped brick. The central bricks were covered with asphalt before being laid, the lower ones are laid in mud and asphalt. The inner imposts are bound together by clamps made of poplar wood soaked in asphalt on a system which can no longer be clearly worked out. The lower ring alone formed an actual arch, each of the two higher rings begin some courses higher than the last and follow only a part of the semicircle, thus forming a segment. They begin nevertheless with a brick laid horizontal and not sloping. It is obvious that the planning of this arch construction is very faulty and inconsistent in comparison with Roman stone vaulting.

The wall stands throughout on a level foundation bed. On the outside it is perpendicular, but on the inside the courses recede a little one behind the other, causing a slight slope and rendering the walls somewhat thicker below than they are above. This batter of the walls never occurs in buildings that are indisputably of the time of Nebuchadnezzar.

On to this old piece of wall, with its three towers to the north and the south, the later walls are built with grooved and tongued expansion joints (see p. 36), for which purpose the old wall was hacked out as far as necessary. The later wall is plain; it formed, however, only a foundation for the now destroyed upper part, which certainly must have been furnished with towers. By this new building the old wall appears to have been strengthened within as by a Kisu, to which the palace walls are closely fitted by means of plain expansion joints.

The lower part of the long northern portion with its seven towers is similar both in age and style of building to the arched door. The upper part is contemporary with the Citadel Gate, and of course the tongued expansion joints are employed throughout, and a powerful strengthening is added on the inside; according to the principles of the ancient architects it was not permissible to rest the footings of this inner strengthening on the lowest level of the foundations, and accordingly there remained in the mesopyrgia narrow spaces that were filled up by small independent walls only one brick thick. Nebuchadnezzar’s architects were very consistent on these points. The gate on the north corresponds with the arched door and is closed with later brickwork. The door in the angle abutting on the Ishtar Gate afforded the entrance to the area enclosed by the two mud walls of the Ishtar Gate. In order to leave this door clear the Citadel wall here in the corner is set back.

The other sides of the Citadel wall we will observe later. The palace must now be studied in detail.