The Etruscans were a people with a distinct language and culture during the period of earliest European writing, in the Mediterranean Iron Age in the second half of the first millennium B.C. They ranged over the Po Valley and some of its alpine slopes, southward along the west coast of Italy, most intensely in Etruria with enclaves as far south as Campania, and inland into the Appennine mountains. Their prehistory can be traced with certainty to about 1000 BC. At their height about 500 BC, they were a significant maritime power with a presence in Sardinia and the Aegean Sea.