GRADO. - The ancient name of G. is *Gradus*, the first port of call for ships bound for Aquileia along the Natisone (as *Gradus Arrensis* = S. Pietro a Grado near Pisa and *Gradus Massaliorum* near Marseilles) and not *Aquea gradatae*; the center of Gradus was at the edge of a cultivated and inhabited countryside, almost entirely free from water and not on an island.
The history of G. properly begins with 568, when the Patriarch of Aquileia, Paul, transferred there before the Lombard invasion of Venetia. But even then it was already a strong and secure place, equipped with places of worship and dwellings; the Byzantine Empire was able to maintain itself there until Venice replaced it during the 8th century. Meanwhile, at the beginning of the 7th century, a new Patriarchate of Aquileia was established in Lombard territory; while at G. the succession of patriarchs continued who could no longer set foot in ancient Aquileia. Thus there arose, a few kilometers apart, two patriarchates, of which that of G. was confined almost exclusively to the island of the same name, though metropolitan over the small Venetian bishoprics that arose along the coast as far as Chioggia. The patriarch was transferred to Venice by Nicholas V in 1451, and the first patriarch there was St. Lawrence Giustiniani, formerly Bishop of Castello. From then on, G. was merely a parish.
Roman walls have been found beneath the basilica of S. Agata, and Roman inscriptions and reliefs come from the lagoon or from demolitions. Within the elongated rectangular city walls (probably 5th century), only partially preserved, three basilicas and three baptisteries can be identified. The Cathedral (S. Eufemia) is a large basilica of Ravenna type, tripartite, with a polygonal apse, built by Patriarch Elias (571-586) on the walls of an earlier basilica, which in turn had been constructed around a small rectangular hall, later misused, with a baptismal font (early 5th century; a sepulchral museum dates from the end of the century). It has the original mosaic pavement, the most extensive of the 6th century, though with large restored areas, and contemporary marble plutei; on either side of the apse are two martyria and to the right the salutatorium, all with fine mosaic pavements. Noteworthy in the Cathedral treasury are two silver caskets (5th and 6th centuries) and a chased silver altarpiece (1372). Smaller is S. Maria delle Grazie, with an apse incorporated into the rectangular plan (5th and 6th centuries); between the two basilicas stands the octagonal baptistery (5th century). Near the southern end of the city walls the basilica of S. Agata has been excavated, dating from the 5th century and rebuilt in the 9th; it too had a baptistery. Near G., on the island of Barbana, is a sanctuary of the Madonna, to which pilgrimages come from all over the region; notable among these are those of the first Sunday in July and the Ausina. - See pl. LXXIV.