The basilica, commonly known as the “Church of Saint Paul”, is the oldest church on the site. It is located 200 m south of the thermal baths and adjoins the fortifications. It was discovered during the excavations of 1924 by the Briton WM Ramsay and  American DM Robinson. As the Acts of the Apostles (XIII, 14-50) mention the coming of Paul and Barnabas to Antioch to preach to the population of the city, in 46 A.D., it is thought that a synagogue was originally built in this place, but archeology does not confirm the presence of it: the building can be dated from the middle of the 4th century A.D.. The mosaics that adorn the floor of the church have geometric and floral patterns, and inscriptions that give the name of Optimus who was bishop of Antioch in 375-381. The church is 71 m long and 27 m wide. It consists of a semi-circular apse with canted sides, a nave separated from the aisles by thirteen columns. The vestibule, to the west of the church, allows access to the nave through a large door and two other smaller ones giving access to the side naves.