According to the sixth-ninth centuries Byzantine literary sources (Justinian’s Novella, Procopius’ Wars and lists of bishoprics of Constantinople, Notitia episcopatuum), Petra was a city fort of historic Lazica and an Episcopal See of the Constantinople Patriarchy. It was built on the order of Emperor Justinian (527-565) to the south border of Lazica, near the sea, on the site of a small settlement called Petra because of rocky relief, and was called Justinian after the Emperor. Owing to its strategic location, Petra played an important role in the sixth century AD, during Byzantine- Persian war for Lazica.
On the territory of Acropolis there have been found fortification constructions situated on two hills and connected to each other with double walls, a small, single-nave church built on the place of a Justinian-time large three-nave basilica, an early Byzantine bath, household constructions (cisterns) and the epoch relevant archaeological artifacts.
Near the Acropolis was discovered a site of a former settlement which contains cultural layers from late Bronze, early Iron, Classical, Hellenistic and early Byzantine periods. Two baths from the 4th century AD, an early Byzantine period villa, a single-nave church of the 6th-7th centuries AD, Christian pit-burials, ancient and early medieval cemeteries were discovered to the north of the fortress, near seaside.
Most of the artifacts discovered in Petra are exhibited in the Batumi Archaeological Museum.