bricks and he developed a canal, which brought water to the work site for the use of both human consumption and the manufacturing of the bricks. Marble was also used to make buildings throughout the city, and marble steps led down to the river's edge.
The basic framework of the city consists of two large semicircles about 19 km (12 mi) in diameter. The city was designed as a circle about 2 km in diameter, leading it to be known as the "Round City". The original design shows as single ring of residential and commercial structures along the inside of the city walls, but the final construction added another ring inside the first. Within the city there were many parks, gardens, villas, and promenades. In the center of the city lay the mosque, as well as headquarters for guards. The purpose or use of the remaining space in the center is unknown. The circular design of the city was a direct reflection of the traditional Persian Sasanian urban design. The Sasanian city of Gur in Fars, built 500 years before Baghdad, is nearly identical in its general circular design, radiating avenues, and the government buildings and temples at the centre of the city. This style of urban planning contrasted with Ancient Greek and Roman urban planning, in which cities are designed as squares or rectangles with streets intersecting each other at right angles.
The surrounding walls
The four surrounding walls of Baghdad were named Kufa, Basra, Khurasan, and Damascus; named because their gates pointed in the directions of these destinations. The distance between these gates was a little less than 1.5 miles (2.4 km). Each gate had double doors that were made of iron; the doors were so heavy it took several men to open and close them. The wall itself was about 44 m thick at the base and about 12 m thick at the top. Also, the wall was 30 m high, which included merlons, a solid part of an embattled parapet usually pierced by embrasures. This wall was surrounded by
