round R3 similar to the rooms round R2. The chemin de ronde, T T´, is on a level with this storey.
Between the main palace block and the eastern fortification wall there lies a group of rooms which is clearly an addition to the original scheme. It is interesting to observe that these rooms are in all essentials of their plan a repetition of the group of rooms to the south of court D. Room U corresponds with the antechamber E; room V with the square room F; W with the cloister J; X, Y, and Z to G, H, and T. But the columns in I I´ are not repeated in the small rooms, Z Z´; room V is covered with a groined vault instead of the barrel vault of F, and the court A is not closed with a wall like the court K. I make no doubt that both these groups of rooms, which are so strikingly similar in arrangement, were intended for the same purposes, and I conjecture that they were ceremonial reception rooms. Herzfeld has compared E and F with the throne room of Mshatta (Der Islâm, loc. cit.).
All the rooms and corridors of the palace are vaulted. Some of the finer vaults are built of brick tiles (for example, over the great hall B and over rooms E, F, I, and I´), but as a rule the vaults are constructed with stones set in mortar, the stones being cut into thin slabs so as to resemble bricks as closely as possible. (Cf. the Sassanian palace of Firûzâbâd, Dieulafoy, L’Art Ancien de la Perse, vol. iv.) All the vaults, whether of brick or stone, are built without centering, and all are set forward slightly from the face of the wall. (The same construction is found at Ctesiphon, see below, Fig. 109.)[83] The groined vault occurs seven times in the corridor C C´ ([Fig. 98]), and it is also found in room V. (See my article in the Hellenic Journal above cited.) The fluted dome over room A is bracketed across the corners of the rectangular substructure ([Fig. 88]). In several cases where a barrel vault terminates not against a head wall, but against another section of barrel vault, it is adjusted to the angles of the substructure by means of squinch arches ([Fig. 99]). A noticeable feature of the vault construction of Ukheiḍir is the presence of masonry tubes running between the parallel barrel vaults ([Fig. 100]). The structural purpose of these tubes is to diminish the mass of masonry between the barrel vaults. Whenever two barrel vaults lie parallel to one another, a tube will be found between them, and similar tubes exist between the vault of the cloister O O and O´ O´ and the outer wall. (See too Fig. 95, which shows a tube between a barrel vault and a straight wall.) Over the vaults of the rooms of the annex in the eastern part of the court, and also over the vaults of the fourteen parallel chambers outside the enclosing wall to the north, a false roof is laid ([Fig. 103]). It serves as a protection against the heat of the sun. Under the eastern annex there are some much-ruined subterranean chambers. A staircase at the south-eastern angle of court D leads down into similar cellars (serâdîb).
The arches over the doorways are usually of an ovoid shape, sometimes slightly pointed. When the door-jambs take the form of engaged columns, the capitals of the columns, roughly blocked out in masonry, carry an arch slightly narrower in width than the opening of the doorway beneath it. But when the door-jambs are formed merely by the straight section of the wall, the span of the arch is wider than the opening of the doorway ([Fig. 102] illustrates both types). This set-back of the arch was doubtless employed in order to facilitate the placing of centering beams. Three wide doorways with round arches, b b´ and c, lead from the main block of the palace building into the surrounding court. The arches are usually characterized by double rings of voussoirs (cf. Ctesiphon and other buildings of the Sassanian and early Mohammadan period), the inner ring laid so as to show the broad face of the stones or tiles, while the narrow end shows in the outer ring. (See the arch in Fig. 102.) The arch construction in the eastern annex is, however, much rougher in style. The outer ring of voussoirs is omitted there, nor is it invariable in other parts of the palace.