Apollonia was an ancient Greek city located on the right bank of the Vjosë river. Apollonia was founded in 588 BCE by Greek colonists from Corfu and Corinth, on a site where native Illyrian tribes lived, and was perhaps the most important of the several classical towns known as Apollonia.
Apollonia flourished under Roman rule and was noted by Cicero in his Philippicae as magna urbs et gravis, a great and important city. Christianity was established in the city at an early stage, and bishops from Apollonia were present during the First Council of Ephesus (431) and the Council of Chalcedon (451).
Its decline, however, began in the 3rd century AD, when an earthquake changed the path of the Aoös, causing the harbour to silt up and the inland area to become a malaria-ridden swamp. The city became increasingly uninhabitable as the inland swamp expanded, and the nearby settlement of Avlona (modern-day Vlorë) became dominant. By the end of antiquity, the city was largely depopulated, hosting only a small Christian community. This community (which probably is part of the site of the old city) built on a nearby hill the church of the Dormition of the Theotokos, part of the Ardenica Monastery.
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.