The palace of Sarvistân bears an obvious relationship to that of Firûzâbâd, but the strict symmetry which regulates the latter is not so closely adhered to, and the construction is handled with greater freedom and skill (Plate 76). The principal lîwân happens, it is true, to have resumed the old latitudinal disposition, but the longitudinal lîwân is present in a subsidiary position. The lateral chambers are provided with wide arched openings which, together with the arch of the lîwân, form a façade not unlike those of the Ukhaiḍir courts.[141] The breaking of the façade by doors leading into the lateral chambers of the lîwân occurs first at Hatra, and characterizes all lîwân buildings later than that of Sarvistân. Instead, however, of the piers and engaged columns of Ukhaiḍir, the three arches of Sarvistân are separated by groups of triple flutes. These flutes are far more clearly connected with ancient oriental tradition than the engaged columns of Firûzâbâd. They are derived from the reed-like flutings of Babylonia and Assyria, which are to be found as late as the Parthian counterfeit at Tellôh.[142] The motive does not disappear after the Mohammadan invasion. It occurs at Kharâneh, a ḥîrah on the western borders of the Syrian desert (see below, Plate 80, Fig. 2), and I found it upon the façade of Sultan Khân, a Seldjuk building in the heart of Asia Minor.[143] Here, as at Sarvistân, it flanks a central doorway. At Sarvistân it gives way at the angles of the palace to a single engaged column. As at Firûzâbâd, the audience hall at Sarvistân is a square domed chamber, but it opens immediately into the posterior courtyard and a single lîwân faces it on the further side. Besides the partial detachment from the wall of the supports of some of the vaults and of the columns bearing the smaller dome, there are other evidences of advance in structural knowledge. In the central lîwân, in the tower chambers, and in the central domed chamber the walls are partially hollowed out by blind niches, which add to the security of the vaults while they increase the interior space of the chambers. These blind niches lend to the supports of the dome something of the appearance of free standing angle piers, and they show a dawning apprehension of the fact that the thrust of the dome is concentrated mainly upon the corners of the substructure. In the isolated dome of Ferâshâbâd[144] the hollowing out of the walls is carried yet further.