Etruscan civilization had its roots in coastal central Italy and was flourishing by 600 BCE. The Etruscans were traders who mined, and sold, valuable minerals such as copper and iron. By 600 BCE, influenced by the Greek model, they formed themselves into twelve city-states, each a political unit. They expanded throughout Italy, beginning with their immediate neighbours, Latium and the land of the ‘Italics Peoples’ (modern Umbria). Wall frescoes and artefacts provide evidence of this early culture. It seems that, like the Romans and Greeks, they were polytheists who also practised human sacrifice. The Etruscans exerted great influence on the early Romans, passing on their institutions and customs, such as the city-state, gladiatorial games and the word, ‘Rome’. By the time of the Etruscan decline c. 550–400 BCE, thought to have been caused by an increasingly dominant Rome and a loss of naval supremacy, Etruscan territories were confined to northeastern Italy and Campania.