In the Period of Four Caliphs in which the movements of conquest continued intensely appeared a new city phenemenon which had the pecularities of being quarters. Basra, Qufa and Fustat which are subjects for our study are cities founded in that manner. The urban structure of these cities took form seemly to the feelings of the citizens who lived here. Because there were neither a foundation nor an authority. In the centre of the city was situated a mosque. Near the mosque were situated social and administrative buildings like a dar al-imara (building of government), a bathhouse, a prison, a bait al-mal (treasure house) and diwans (houses of council). Commercial activities were kept together around the mosque. Factions were made according to species of goods in bazaars. From the centre to the suroundings were spread a lot of mainroads . In every districts of the city a tribe or a group of tribes resided. Some sort of dwellings were detected in the cities. These were formed in pursuance of the social structure.