The church of St. Sergio (also known as St. Sergius or Abu Serga) was built in the centre of the Ancient Roman fort of Babylon. The church is considered as one of the sites visited by the Holy Family during their escape from King Herod to the land of Egypt.

The church most probably dates back to the 5th Century, although some historians believe that it was actually built in the 8th Century. We are not sure of the origin of Saint Sergius, as in the history of the Coptic Church there are two Saints with the same name. The first one was an Egyptian who died, together with his father and sister, during the intense Christian persecution. People today celebrate his memory every year on the 7th of February. The second one was a servant of the Roman Emperor Maximilian, and he was martyred in Syria at the beginning of the 4th Century.

The Church takes the shape of a basilica with a narthex, a nave, and 2 aisles, which are separated from the nave by 12 columns with Corinthian capitals, 10 of stone, one of marble and one of rosette granite. There are 3 Sanctuaries on the east side; each Sanctuary contains an altar, with a wooden dome, supported by 4 marble columns. The dome of each altar has religious scenes of Christ, Angels, and the 4 evangelists. There is a pulpit on the northeast side of the nave, which is made of marble, though originally it was made of wood, incrusted with ebony and ivory.

The pulpit is used once, each year, in the prayer of Great Friday. The central Sanctuary has a wooden screen, which dates back to the 13th Century, incrusted with panels of ebony and ivory. The frieze and the icons of the church are remarkable, most date back to the 15th and 16th Centuries, some were damaged and restored later.

One of the most important locations in this church is the cave in which the Holy Family stayed during their journey into Egypt. It has a nave and 2 aisles and the ceiling is domed. At the end of the southern aisle of the Cave, is a baptistery.
On the 1st of June, each year, the church of St. Sergio commemorates the arrival of the Holy Family by having prayers inside the church of the cave.