Bar was a well developed settlement in the 6th century, and there is some proof that the development if the town started precisely at this time. This is because if the discovered remains of the oldest basilica in the town, dedicated to St. Theodore the Warrior. The church was ereected on a plateau, where later the larger Romanesque church of St. George was built. During the excsvstion, in the same place, the remains of a mosaic from the 5th - 6th century were discovered, as well as some graves made of roofing tiles. In one of the graves a "Dove" type fibulla was discovered which most probably originates from the 7th century. A small post from the altar which was discovered also belonged to this church. It is decorated with motifs of vines and kantharoskantaros, a Greek drinking cup, a symbol of the Eucharist.
The basilica must have been a part of the fort, so it is probably that Bar could identified with the Antipargi settlement, mentioned by the Byzantine historian Procopius of Caesarea.
Beneath the gate, ercted in the 8th-9th century there are remains of a square biulding, perhaps the original tower of the late antique fort.
In the towns citadel remains of a house which burned down in a catastrophic fire were discovered. This could indicate the invasion of Avars, who ransacked Dalmatia at the end of the 6th and the beginning of the 7th century. Inside the hearth, scores of fragments of various pots made using the fast-wheel technique were discovered. The pots are Byzantine in style, and a large number of amphora, plate and jug pieces werre also found, dating from the 5th tot the 7th century, originating from northern Africa and Greece.
During the 7th century Bar was populated by Roman refugees from conquered Duklj, in the places where the people living by the sea were already settled. The most reliable archaelogical testimony to the existence of a town complex in this period is the excavated late antique piece of cobbled road from the 5th or 6th century which today stand outside St. John's Church. On the surface of the discovered piece of cobbled road, there were numerous fragments of btick, 5th century amphorae and animal bones, and all of them were covered in a layer of soot which abruptly ended this horizon of life.
The settling of the Slavs in the 7th century started to grdaually change the ethnic picature in the area. At the beginning, the Slavic groups startet to take part in the everyday life within the walls.
The final christianisation of the Slavs ended in the middle of the 9th century. During this period, many Paleo-Byzantine churches were restored, including St. Theodore's Church, which received new furniture in the spirit of pre-Romanesque art. The typical decorations of the iconostases during this period include the engravings of ornaments in the shape of three-way interwoven decorations, as a shallow relief, which is the main characteristic of this type of sculpturing. In Old Bar, scores of finds from pre-Romanesque reliefs were discovered.