The famous Western former patriarchate of Aquileia has its episcopal see in Aquileia, a city of the Roman Empire, situated at the head of the Adriatic, on what is now the Italian sea-coast, in the autonomous region Friuli-Venezia Giulia (former Habsburg country of Goerz / today it. Gorizia, sl. Gorica), at the confluence of the Anse and the Torre, for many centuries, and as such played an important part in ecclesiastical history, particularly in that of the Holy See and Northern Italy.
Ancient tradition asserts that the see was founded by St. Mark, sent thither by St. Peter, previous to his mission to Alexandria. St. Hermagoras is said to have been its first bishop and to have died a martyr's death (c. 70). At the end of the third century (285) another martyr, St. Helarus (or St. Hilarius) was bishop of Aquileia.
In the course of the fourth century the city was the chief ecclesiastical centre for the region about the head of the Adriatic, afterwards known as Venetia and Istria. In 381, St. Valerian appears as metropolitan of the churches in this territory; his synod of that year, held against the Arians, was attended by 32 (or 24) bishops.
In time, part of Western Illyria, and to the north, Noricum and Rhaetia, came under the jurisdiction of Aquileia. Roman cities like Verona, Trent, Pola, Belluno, Feltre, Vicenza, Treviso and Padua were among its suffragans in the fifth and sixth centuries. As metropolitans of such an extensive territory, and representatives of Roman civilization among the Ostrogoths and Lombards, the archbishops of Aquileia sought and obtained from their barbarian masters the honorific title of patriarch, personal, however, as yet to each titular of the see. This title aided to promote and at the same time to justify the strong tendency towards independence that was quite manifest in its relations with Rome, a trait which it shared with its less fortunate rival, Ravenna, that never obtained the patriarchial dignity.
It was only after a long conflict that the popes recognized the patriarchal title thus assumed by the metropolitans of Aquileia. Owing to the acquiescence of Pope Vigilius in the condemnation of the "Three Chapters", in the Fifth General Council at Constantinople (553), the bishops of Northern Italy (Liguria and Aemilia) and among among them those of the Venetia and Istria, broke off communion with Rome, under the leadership of Macedonius of Aquileia (535-556).
In the next decade the Lombards overran all Northern Italy, and the patriarch of Aquileia was obliged to fly, with the treasures of his%