Aquileia was founded by the Romans in 181 a.C. receiving the Ius Latii, which marked it as a friend and allied of Rome, although with a lower legal rank than the colonies of Roman veterans/citizens. Ninety years later Aquileia gets the status of Roman municipality, evidence of a great economic prosperity based on its condition of starting point of several first-class commercial routes and also in its privileged geographical situation: very close to the confluence between the eastern and western halves of the Empire.
During the 2nd and 3rd centuries AD it stands as the main city in northern Italy and the nearby illiric area. Up to 100,000 inhabitants would live in Aquileia at this time, acting the city both as economic engine of a vast region and as first order stronghold: true key to access to the Italian peninsula by any invader from the north and east. This prosperity would continue during the Late Empire, manifesting itself in the construction of a large number of magnificent buildings among which stood a superb imperial palace, under whose walls Constantine I stayed with some frequency. Unfortunately the arrival of the dreadful 5th century would bring serious disturbances to the great Adriatic city: for its misfortune forced to serve as an advanced defense against the multiple invaders who longed to penetrate the Italian peninsula to plunder its still intact riches. Effectively, in the year 401 and again in 408 Aquileia must withstand two sieges by the vandals of King Alaric, falling finally in 452 before the fierce Huns of Attila. The destruction that followed this conquest was so complete that the city never again recovered even a fraction of its former splendor. In fact the majority of the survivors of the brutal sacking moved to a zone of lagoons located to 13 kilometers, founding a establishment that by its eminently lacustrine character was very difficult to attack by invaders like the Huns, based on massive forces of cavalry. This settlement would give rise over time to the magnificent Venice, whose lordship over the region would remain unchallenged for many centuries, reducing the classical Aquileia (or rather what was left of it) to the status of small feudal village dependent on Venice.