The old town centre of Grado is mainly the old "Castrum", that is the first urban centre that had been fortified in the first decades of the 5th century; a narrow area that developed during the Imperial Age as the extremity of the Port of Aquileia.
The old town centre is very interesting because of its picturesque architecture that houses a group of monuments of great artistic value: the Duomo, the Basilica of St. Eufemia, the Baptistery and the Basilica of Santa Maria delle Grazie. These important holy buildings along with the ruins of another basilica and baptistery which had been discovered under the Piazza della Vittoria, are connected to the presence in Grado of the bishop and the presbyters of Aquileia, who had taken shelter here after the Longobard invasions.