During the first millennium BC, the geography of southwest Iberia, its coasts and internal territories were the set for a complex historical process that involved indigenous populations, Phoenicians, Greeks and Carthaginians that resulted in the ethno-cultural mosaic about which Greek and Roman authors have reported. This chapter focuses on connection routes, forms of contacts and interaction between landscapes and human groups and the different levels of socio-economic and politico-ideological complexity that developed over time. It begins with the Tyrian foundation of Gadir, as this town would later become the centre of an extensive network of inter-regional relations, articulated around primary centres such as Huelva, lower Guadalquivir, as well as coastal and interior peripheries such as south-central Portugal, Extremadura, southern Meseta and upper Guadalquivir. The chapter explains the sixth-century crisis and its impact on coastal southwest Iberia. In time, the entire southwest was reoriented towards Rome and underwent profound political, socioeconomic and cultural reorganisations usually captured by the term Romanisation.