The great hall, to the south of room 4, is the largest chamber in the palace. It is 15·50 metres long by 7 metres wide, but its width is increased on either side by arched recesses 1·40 metres deep and from 2·20 metres to 2·30 metres wide (Plate 14, Fig. 1). These recesses, five on either side, are separated from one another by squat engaged columns set against piers which are ·80 metre deep. The columns carry rectangular impost-capitals from which spring the shallow slightly pointed semi-domes, or calottes, which cover the recesses. The capitals are very roughly constructed of small stones. There are traces of a shallow abacus, while a cavetto moulded in plaster seems to have been interposed between capital and shaft. At the corners a triangular stone adjusted the circle of the column to the square of the abacus, and the whole was no doubt covered with plaster. The abacus projection runs back along the walls of the niche and above it the calotte springs from another small projection (Plate 15, Figs. 1 and 2). The calottes are bracketed over the angles, the construction being the same as that described in the dome of room 4. All the niches of Ukhaiḍir are treated in like fashion. The method employed in constructing the archivolts is admirably described by Dr. Reuther.[17] The face of the arch is formed by a permanent centering composed of gypsum and reeds. The vaulting takes place, not above the centering but between the two centering arches, the vault being built in vertical rings (Fig. 2). When the arches are of wide span an outer ring of horizontal voussoirs is added to the inner arch. This system is common in Mesopotamia to the present day, and is found frequently at Ukhaiḍir. In the great hall there are holes for wooden beams below the abacus of the capitals and in the spandrels of the arches. The northern recess on the east side is open and gives access to a ramp which leads to the first floor. The second, third, and fifth recesses contain low doors covered by a segmental arch. On the west side similar doors are set in the first, third, fourth, and fifth recesses, the last named giving access to a stair (Plate 15, Fig. 2). The calotte archivolts at their highest point are 3·50 metres above the present level of the floor. The wall is carried up for another 1·25 metres, where there is a double outset from its face. Above this outset the stone vault runs up perpendicularly for about ·80 metre and the remainder of the vault is of brick (Plate 14, Fig. 2). For a height of about 1·50 metres the brick tiles are laid horizontally, but when the curve of the vault increases the bricks are set upright in vertical rings. The vault thus formed is built without centering; it has a slightly pointed, ovoid shape and is much stilted. The north wall remains intact and its scheme of decoration is instructive (Plate 16, Fig. 1). The arched door, 3·50 metres high, is set back within a niche 1 metre deep.