Canal Grande dall' Accademia - Early photography, Public domain image

Many historians agree that the original population of Venice consisted of refugees from Roman cities near Venice such as Padua, Aquileia, Treviso, Altino and Concordia (modern Portogruaro) and from the undefended countryside, who were fleeing from waves of Germanic and Hun invasions. Between year 166 to 168, the Quadi and Marcomanni destroyed the main center in the area, the current Oderzo. The Roman defenses were again overthrown in the early 5th century by the Visigoths and, some 50 years later, by the Huns led by Attila. The last and most enduring immigration into the north of the Italian peninsula, that of the Lombards in 568, left the Eastern Roman Empire a small strip of coast in the current Veneto, including Venice.