ABSTRACT
Throughout the arid zone, oases have developed wherever reliable water supplies have permitted permanent settlement. The size of the settlement which has come into being depends on many factors, such as communications, a fertile hinterland and security, though perhaps the most important is the volume of water available. In the West the most common image of an oasis consists of a small pool of groundwater, set amongst date palms and surrounded by small white flat-roofed houses. A camel or two and people in flowing robes would complete the picture. Such oases do, of course, exist throughout north Africa and the Arabian Peninsula. Their importance normally lies as staging posts along lines of communication and trade. Much more important, though, are the oases which have given rise to major urban centres. These are often found in inland locations and are watered by a major river or series of smaller streams. For them to be prosperous large areas of fertile land have to be located nearby. In the Old World, Damascus, Isfahan, Samarkand and Kairouan stand out, while in the New World, Salt Lake City, Phoenix and Tucson provide recently created examples.
