Aquileia (in Friuli-Venezia Giulia), one of the largest and wealthiest cities of the Early Roman Empire, was destroyed by Attila in the mid-5th century. Most of it still lies unexcavated beneath the fields, and as such it constitutes the greatest archaeological reserve of its kind. The patriarchal basilica, an outstanding building with an exceptional mosaic pavement, played a key role in the evangelization of a large region of central Europe.
Aquileia was founded by the Romans as a Latin colony in 181 BC in the north-eastern corner of the plain of the Po at the northern end of the Adriatic. It communicated with the sea by means of the Natissa (Natiso) river. Originally conceived as an outpost against Gallic and Istrian barbarians, it quickly became a major trading centre, linking central Europe with the Mediterranean. Among the goods that it traded through its great river port were wine, oil, furs, iron, and slaves. It was also the southern terminus of the amber route, dating from prehistory, and this prized product from the Baltic was worked by Aquileian craftsmen for sale throughout the Empire. High-quality glassware became an important manufacture following the establishment of a workshop there in the 1st century AD by the celebrated Phoenician craftsman Ennion.
By 90 BC it had been elevated to the status of municipium and its citizens were accorded full rights of Roman citizenship. Its wealth resulted in the town being endowed with many magnificent public buildings, and the private residences of its rich merchants were opulently decorated. It is estimated that its population had reached over 200,000 by the end of the 1st century BC. During the 4th century Imperial residences were built in Aquileia, and it was the seat of an Imperial mint between 284 and 425 AD. Of especial importance was the construction in the second decade of the 4th century of a basilica by Bishop Theodorus, following the sanctioning of public worship by the Edict of Milan in 313.
All this was to come to a violent end in 452, when Aquileia was sacked by the Huns led by Attila. The survivors clustered in a drastically reduced settlement around the Basilica, in the area of the small present-day town, which occupies only a fraction of the Roman city. Its mercantile role was assumed later by Venice, which provided a similar trading link between central Europe and the Mediterranean. However, Aquileia retained its spiritual significance, becoming the seat of a patriarchate whose territory extended westwards as far as Como and embraced a large area of modern Austria, Slovenia, and Croatia. The Patriarchate of Aquileia, which survived until 1751, played a key role in the evangelization of this region and the great Basilican Complex still serves as its spiritual centre.