Before Islam, the African Sahara, had witnessed the spread of significant types of desert architectural constructions, namely residential fortified settlements known as "Qusur". The spread of Islam in Maghreb countries had a positive effect on the commercial activity between the north and south of the African Sahara. Consequently, these residential settlements or "Qusur" have turned into active trade centers that extended along this Sahara.Al-Qusur Al-Sahrawiyahhave received particular attention on the part of many researchers in the field of the history of architecture. This attention was developed within the framework of descriptive analytical and comparative studies of the layout and planning of this type of constructions that sought to highlight the similarities and differences among them. However, it is noticed that these studies covered only a small number of those constructions compared to their great number as they spread throughout the Algerian Desert and other regions of the African Sahara.Therefore, the present paper reviews the features of the urban planning of QasrOuargla in the South-East of the Middle Maghreb Desert as one of the most important desert urban settlements. These settlements played significant roles in the history of this region and Algeria in general all over the stages of its Islamic history up till now. This Qasr has incorporated all the essential elements of urbanization, as it had all means of fortification such as trenches, walls, towers and gates. Furthermore, the Qasr had a government headquarter, military garrison fortress represented by the "Qasaba" and a mint. It was also an outstanding trade and economic center among Al-Qusur Al-Sahrawiyah in Algeria. This study is particularly significant as this Qasr still maintains a great deal of its architectural constructions and it is still populated while many other Al-Qusur Al-Sahrawiyah have been deserted and become extinct.