The region of West Africa lying between the Volta river and Lake Chad, comprising in modern political terms Nigeria and the immediately adjacent countries of Bénin, Niger and Cameroon, was probably, even by the thirteenth century, one of the best-populated parts of the entire continent. It lay at the meeting-point of Africa's three main language families. It had been the scene of the earliest metalworking, in both copper and iron, anywhere to the south of the Sahara. It had therefore probably witnessed the earliest intensive agriculture made possible by forest clearance with iron tools. While it had experienced no concentration of political power on the scale of the empires of Mali and Songhay in the west, it was, even more than its western counterpart, a region in which most people lived in defended towns, from which they went out by day to till their farms in the surrounding countryside. Buildings, wherever it was climatically possible, were of puddled clay and, when these were damaged by weather or warfare, they could normally be rebuilt on the same sites, using the same materials. Urban settlements therefore enjoyed a relative permanence unusual in other regions of Africa, and these settlements, together with their surrounding farmlands, formed the basic units of government. On a wider basis, small towns might pay respect to larger ones, and newer towns might honour the older towns from which their founding ancestors were supposed to have come.