Based on extensive architectural and archaeological research, these papers present a series of studies on the art, buildings, settlement patterns, and land use in Iraq, Yemen and Oman, from the pre-Islamic period to modern times. Many of the monuments and sites were studied here for the first time, and have subsequently disappeared or become inaccessible. Among the main themes emerging from Professor Costa's work are the continuity of Arab craftsmanship, in both technical and aesthetic terms, from Late Antiquity into the Islamic period; the relationship between the natural and the built environment; and the dependence of architecture and settlement patterns on the exploitation of natural resources, especially water.

An extensive survey of the architecture and decorative features of mosques and other religious buildings in Oman which, Costa argues, contains buildings unlike those found elsewhere in Islamic Arabia. Individual mosques are described in detail, accompanied by numerous photographs and plans, with a discussion of the different influences that affected the architecture of each region of Oman, including the strong Portuguese influence.