The Iberian Peninsula began to take on its role as a crossroads. The migrations and trade dealings with other peoples shaped a series of relatively independent civilisations, distinguished into three main groups –Celts, Celtiberians and Ibers– each with its own cultural traditions and technological skills, and its own economy. These centuries prior to Rome’s conquest of Spain saw the appearance of the first urban settlements –fortified villages, and towns such as Numancia– and the first stable social and political structures.