The fortress was built between the years 969 – 976, during the reign of the Byzantine emperor Ioan Tzimiskes, and was a solid construction,being thus the only fortress of the Byzantine Empire in Europe that has stood the test of time.
In 976, after the death of Emperor Ioan Tzimiskes, the Byzantine rule in the south of Dobrudja had been violently removed by the Bulgarians, only to return again around the year 1000, the evidence of byzantine life inside the city being evident. Throughout the time, the Byzantine fortress went through a flourishing economic period, especially between the XIII – XIV centuries, but in the years 1421 – 1422 its activity was stopped, the reason for this being unknown.
The fortress initially occupied an area of 5-6 hectares and probably had a trapezoidal shape. Historians believe that the it had the role of customs and defense, having a special importance during the Byzantine rule in Dobrogea. The fortress represented the headquarters of the imperial war fleet and the military garrison.
The durability of the walls of the fortress was given by a special technique used during the construction, called the wooden substructure, which was used due to the positioning of the fortress on an alluvial field. The walls were built of shaped stone blocks, the gate on the north side having obvious Byzantine influences.
After some archaeological that started in 1956, some very important complexes were discovered. On the eastern side there is a jetty with docks, docking places, etc., having a width of 24 m and being bordered by two rectangular towers; a 4-meter wide gate; and a building with an apse.
Currently only 10-15% of the fortress is visible. The water is affecting it more and more, and through the works carried out over time on the Danube, the erosion process has been accelerated. Solutions for the recovery and inclusion of the ancient fortress in a tourist circuit exist, but this would require a huge financial effort.