Saint Paul's visit to Philippi (AD 49) laid the foundations for a distinguished bishopric and a flourishing Christian community (extensive Christian cemetery with a cemetery basilica extra muros dating from the second half of the 4th c. AD).
In the middle of the 4th century, Porphyrios, the bishop of Philippi (312-342), built a house of prayer dedicated to Saint Paul, as part of a complex consisting of a baptistery, bishop's residence and a spring. On the site of this, in the 5th c., was built the Octagon, a building unique in Greece.
Although Philippi was threatened, fatally, by Ostrogoth raids (473-483), it acquired one of the largest Early Christian basilicas (Basilica A) in the late 5th century. In the middle of the 6th c. a unique domed basilica (Basilica B), which had a movable font, was built to the south of the Roman forum. The three-aisled Basilica C, another 6th century building, was destroyed by earthquakes (610-620).
Raids by the Slavs (7th-8th c.) were followed by those by the Bulgars (9th c.), obliging the Byzantines to fortify Philippi and its acropolis (963-969). In the 9th century, the bishopric of Smolena in the area of the by now Hellenised Slavs, was assigned to the archdiocese see of Philippi, which was already responsible for six other bishoprics.
With its port at Chrysoupolis (modern Kavala), Philippi was the scene of intense commercial activity (the commercium was exacted here, because of its location on the Via Egnatia), and viticulture was also practised. The city was gradually abandoned after the Ottoman conquest (1387).