Qaser Libya known as the Old Olbia as it was referred to in the Sinesio ( Bishop of Cyrene ), letters in the 5th century A.D, was also the residence of the Bishop. It has two churches of great religious interest. The western side known for its extraordinary architecture and the eastern side for its splendid 50 mosaic pieces which originally came from the floor of the western basilica and depict a wide range of subjects including animals and crucifixes made from precious stones.

The panels are in a splendid condition and one depicts the only existing representation of the Pharos-Lighthouse of Alexandria- one of the seven wonders of the ancient world. Later on during the Turkish period the eastern church was transformed into a fort.