From central Syria, where it forms the interfluve between the Euphrates and Tigris rivers to the shores of the Indian Ocean, and from the Red Sea to the Persian/Arab Gulf, there extends the vast platform of Arabia - a block of ancient rocks that appears as a massive detached fragment between the even larger Kraton of Africa, and the fold systems of Iran and Asia Minor. Parallel to the overall structural unity is a climatic uniformity: apart from marginal exceptions in the extreme south-west, annual rainfall nowhere exceeds 250 mm, with at the same time some of the highest temperatures (and extremes of ultra-dry to inordinately humid air) of anywhere in the world. Such physical unity has had an effect on the human geography of the region. From Arabia has arisen the special way of life spoken of as ‘ A rab ’ ; and though in the main a thoroughly arid plateau environment may appear harsh, yet human activities in neighbouring lands and far beyond have been and are still conditioned by life in the Peninsula, which remains the centre of thought, pilgrimage and aspiration for many millions in Asia and Africa. Arabia thus emerges as the major core, or heartland, of the Middle East.