Aquileia is an ancient Roman city in Italy, at the head of the Adriatic at the edge of the lagoons, about 10 kilometres (6 mi) from the sea, on the river Natiso, the course of which has changed somewhat since Roman times. Today, the city is small, but it was large and prominent in classical antiquity as one of the world's largest cities with a population of 100,000 in the second century AD and is one of the main archaeological sites of northern Italy. In late antiquity the city was the first city in the Italian Peninsula to be sacked by Attila the Hun.