Since prehistoric times, Greeks, Etruscans and Celts have inhabited the south, centre and north of the Italian peninsula respectively. The very numerous Rock Drawings in Valcamonica go back to 8,000 BC, and there are rich remains of Etruscan art from thousands of tombs, as well as rich remains from the Greek colonies at Paestum, Agrigento and elsewhere.  Ancient Rome finally emerged as the dominant Italian and European power. The Roman remains in Italy are of extraordinary richness, from the grand Imperial monuments of Rome itself to the survival of exceptionally preserved ordinary buildings in Pompeii and neighbouring sites. Following the fall of the Roman Empire, in the Middle Ages Italy, especially the north, remained an important centre, not only of the Carolingian art and Ottonian art of the Holy Roman Emperors, but for the Byzantine art of Ravenna and other sites. Arab-Norman Palermo and the Cathedral Churches of Cefalù and Monreale reflect the influence and craftmanship of the Islamic populations of Sicily and the south.