In the 6th century, under the Byzantine emperor Justinian I, it served as an important Eastern Roman outpost in the Caucasus and, due to its strategic location, became a battleground of the 541–562 Lazic War between Rome and Sasanian Persia (Iran).

It was built to reinforce the Roman authority in the kingdom of Lazica, located on the southeastern shores of the Black Sea and, with the emperor's approval, was named in his honor as Petra Pia Justiniana.

In 541, Khosrow, following an initial unsuccessful assault on the fortifications of the city, captured Petra by sending his troops through a secretly constructed tunnel and destroying the towers, which induced the Romans to capitulate.

[11] Mainstream scholarly opinion identifies Petra with a ruined settlement found in the village of Tsikhisdziri, in Georgia's southwestern autonomous republic of Adjara, between Batumi and Kobuleti.

There are some modern scholars who have rejected the identification of Petra with the Tsikhisdziri site, such as Simon Kaukhchishvili, a translator and critical editor of the Byzantine sources on Georgia, and Guram Grigolia.