Aquileia, one of the largest and wealthiest cities of the Early Roman Empire, was destroyed by Attila in the mid-5th century. 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.
The architectural development of the Basilica of Aquileia, dedicated to the Virgin Mary and the saints Hermagora and Fortunatus, started immediately after 313 AD. In that period the Edict of Milan put an end to religious persecution and the Christian community was legally able to build its first place of public worship. In the following centuries, after the destruction of this first church, seat of a bishopric, the inhabitants of Aquileia built it up again other four times, using each time the structures of the previous buildings: Theodorian Hall, first half of the 4th century; Post-Theodorian North, middle of the 4th century; Post-Theodorian South, end of the 4th century or after the middle of the 5th century; hall of Maxentius, 9th century; Poppo's church, first half of the 11th century; rebuilding of the upper part of the church by Markward von Randeck, from the pointed arches to the roof, 14th-15th century.
The Basilica, as it is today, is in Romanesque-Gothic style. The entire floor is a wonderful coloured mosaic of the 4th century, brought to light in the years 1909-1912. With its 760 square metres the floor is the largest Paleo-Christian mosaic of the western world. The mosaic was partly damaged due to the construction of the columns flanking the right side at the end of the 4th century according to some scholars and after the middle of the 5th century according to others.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.