To the same group belong a small ruined bath at ‘Abdeh[253] and the bath at Rḥaibeh,[254] the first being possibly Byzantine. At ‘Abdeh the dome placed between two semi-domed niches is set on horizontal brackets. In the palace of Qaṣr ibn Wardân the dome between two semi-domed niches is the basis of the plan, but it is further elaborated by the placing of a semi-domed chamber on the alternate sides. These two chambers are not, however, an integral part of the domed chamber, for they are separated from it by solid walls broken only by doorways. Fortunately we are not reduced here to conjecture concerning the date. On the lintel of the south gate an inscription gives the year A.D. 564.[255] It is clear, therefore, that the dome between semi-domed niches is an architectural scheme which was taken over by the builders of the Mohammadan age from their Byzantine predecessors, and all the evidence points to the conclusion that in both periods the artificers were Syrians. Al-Ṭûbah is the southernmost of the Wâdi Ghadaf palaces[256] (Fig. 28). Its plan is that of Qasṭal repeated three times, with the addition of projecting rectangular chambers on either side of the gates. When the three main courts adjoin one another the side chambers against the dividing walls are omitted. The individual baits are very similar to those of Qasṭal, but only one row of chambers is interposed between each of the small courts. Thus at first sight it looks as if the Ṭûbah bait consisted of a court with rooms on one side only, except in the north-east and north-west angles, where the courts have chambers on both sides, that the corner spaces may be filled in. Actually, however, the [Illustration: FIG. 28. Ṭûbah. (From _Qṣeir ‘Amra_, by kind permission of the Akad. der Wiss. in Vienna.)]