From 724-7 the Umayyad Caliph Hisham constructed Qasr al-Hayr al-Gharbi, the remains of which are located approximately 37 miles west of Palmyra. Like its sister site, Qasr al-Hayr al-Sharqi, the settlement features an impressive irrigation system complete with a complex network of underground canals originating at a Roman dam (Harbaqa) about ten miles to the south. An outer wall measuring 1,050 by 442 meters and constructed of mud brick over a masonry foundation protected this arable land and the rest of the settlement that includes a khan, a palace and a bathhouse. Semicircular towers that alternate between its exterior and interior support this outer structure.
Built in mud brick over stone, the khan measures almost 55 sq meters. It is organized around a central courtyard that continues into a 2.5-meter deep portico and is surrounded by three long rooms that each extends the length of the northern, western, and southern walls and six individual rooms to the east. Its main entrance is situated at the center of this façade. In addition, both the northern and southern exterior walls expand outward at the northeast and southeast points of the building. To the north, this extension provides a drinking trough behind a three columned portico while to the south it served as a small rectangular mosque (the remains of a mihrab have been found at the site). One significant feature of the khan is an inscription carved into a lintel verifying the date and the commission of the site under Hisham. Executed in the ancient Roman tradition, this inscription would have read in bronze castings slightly indented into the stone and secured with metal pegs.
The palace at Qasr al-Hayr al-Gharbi is also square in plan with each wall measuring approximately 70 meters. Its main entrance is situated on the eastern façade and is encompassed by two semicircular towers. Stuccowork from this front façade can be found today in the Damascus Museum. In addition, a circular tower supports each corner of the building except the northwest one which is defined by a stone rectangular tower, the remnants of a 6th century Byzantine monastery. Three other semicircular towers buttress the center of the northern, western, and southern walls. The exterior consists of a stone foundation; over which is an area of baked brick and then mud brick. The gate extends into a corridor that opens into a portico and then a central courtyard by way of a small step. Suite-like areas, each accompanied by their own latrine, surround the court on two stories and similar in plan. Frescoes adorn two rooms of the palace, painted onto the floor.
North of the palace almost 30 meters, the bathhouse is constructed of stone. It consists of a heated marble area, an unheated area covered with plaster to mimic marble, and two service sections. It features barrel-vaulted rooms and a lateral heating system.
Creswell, K. A. C. A Short Account of Early Muslim Architecture, 135-149. Rev. ed. Allan, James W. Aldershot: Scolar Press, 1989.