from northeastern Syria have migrated to the city, mainly for economic reasons. Like the agrarian Sunni clans of the plains, the Druze in Jabal Hauran were traditionally organized in a hierarchical clan order that saw a disparity in the distribution of social influence and prestige. The Bani al-Atrash are the leading clan and predominate in some sixteen towns and villages, mostly in the southern parts of Jabal Hauran. In the northern parts, the Bani 'Amer predominate in eleven villages, while the other major clan in the northern Jabal Hauran was the Halabiya family. Though the Bani al-Atrash and Bani ‘Amer were the more powerful clans in the governorate, members of the Banu Assaf of Attil, Salim and Walghah and Bani Abu Ras of al-Ruha historically dominated the judiciary, while the Hajari, Hinnawi and Jarbu families historically provided the Druze community's religious leadership in Qanawat. Architecture The Hauran has its own vernacular architectural tradition, known as the Hawrani style, which is characterized by a number of distinctive factors. One of these is the exclusive use of basaltic stone for building material. Known for its hardness and black color, basalt is readily available throughout the region and until recent decades, was used for nearly all construction work done in the Hauran. Due to a lack of timber, basalt took the usual place of wood and was used for doors, window seals and ceilings. The reliance upon basalt in the Hauran "formed a truly lithic architecture“, according to the architectural anthropologist Fleming Aalund. The tensile strength of basalt enabled the "development of unusual building techniques", according to historian Warwick Ball. Among these methods was the cutting of long, narrow beams from basalt to roof large areas spanning or longer. Because of the size restrictions of the beams, a distinctive system of traverse, semi-circular arches was devised to support the roof. Corbels, typically no longer than , were used to expand the intervals between the arches and the walls. This method "gave rise to the distinctive, cantilevered 'slab and lintel' architectural style that is peculiar to the black basalt areas of the Hauran", according to Ball. The fusion of Nabatean, Hellenistic and Roman styles also characterizes the architecture of the region. Hawrani-style architecture is dated to at least the 1st century CE, when the Nabateans moved their capital from Petra to Bosra. The Nabateans were avid builders who had their own distinctive architectural tradition.