Firûzâbâd affords the earliest extant example of the dome in Persia. In Babylonia and Assyria no dome is standing which can be dated earlier than Ukhaiḍir. Possibly the Lakhmid ḥîrahs would have provided us with other instances, but the tentative nature of dome building at Ukhaiḍir throws doubt upon the proficiency of Lakhmid construction in this respect.[131] In the Babylonian cultural sphere the dome does not seem to have played an important part in monumental building until a late period, and in my opinion too much significance has been attached to the celebrated relief exhibiting domed buildings which Layard found at Quyundjik.[132] We have here a representation of village architecture, and it is natural to suppose that the domes were of small dimensions. They are to be found to this day in the village architecture of northern Syria and northern Mesopotamia, indeed no other form of roof exists; and they take the shapes depicted upon the relief. They are built of sun-dried brick held together by a mortar of clay. The high ovoid domes which appear upon the relief and in modern villages are built of oversailing rings, like the solitary dome at Hatra. I imagine that the summit of the round domes is constructed over a light centering, but I have not actually seen them in process of being built. The difficulties presented by these methods are practically nil, owing to the light and malleable material and the smallness of the span. The translation of this primitive dome into larger diameters was a very different matter, and there is no evidence for the belief that this step was taken in Mesopotamia in an early age.