The Sumerian city of Eridu, on the coast of the Persian Gulf, is considered to have been the world's first city, where three separate cultures may have fused — that of peasant Ubaidian farmers, living in mud-brick huts and practicing irrigation; that of mobile nomadic Semitic pastoralists living in black tents and following herds of sheep and goats; and that of fisher folk, living in reed huts in the marshlands, who may have been the ancestors of the Sumerians.