Sardinia is an island in the Mediterranean Sea and an autonomous region of Italy. The site of the Nuraghic civilisation in prehistory, the island passed to Phoenician and then Roman rule. Upon the collapse of the Roman Empire Sardinia was occupied by the Vandals and later by the Byzantines, but foreign rule quickly eroded and by the 9th century the Byzantine representatives had formed their own autonomous states. By the end of the Middle Ages however, the Aragonese had established dominance over the island. In 1718 Sardinia was handed to the house of Savoy, and it became a constituent part of the Kingdom of Piedmont-Sardinia, which eventually led Italy to its national unification in 1861.