The Christian monuments of Thessalonika are outstanding examples of churches built according to central, basilical and intermediary plans from the 4th to the 15th centuries. For this reason, they constitute a series which is a typological point of reference. The influence of the Thessalonian churches on the development of the monumental arts was considerable, first in the Byzantine and later the Serbian world, whether in the early Christian period of the high Middle Ages or the Palaeologan Renaissance. The mosaics of the Rotunda, St Demetrius and St David's are among the great masterpieces of early Christian art.
Thessalonika was founded in 315 BC by Cassander, who named it after his wife Thessalonik, just a short time after the new cities of Alexander. Following the Roman conquest of Macedonia, it became one of the Empire's provincial capitals. A cosmopolitan and prosperous seaport, the city grew in commercial and strategic importance during the Roman period and was one of the first bases for the spread of Christianity. St Paul first travelled there in AD 50, and he returned in 56 to visit the church he had founded and for which he exhibited great concern in his Epistles.
Imperial splendour and the changing fortunes of the Thessalonian church were inextricably linked during the early centuries of Christianity. It was during the period that the palatial complex of Galerius was being built (298-311) that St Demetrius was martyred (c. 303). Some time later the rotunda, which Galerius had probably planned as his mausoleum, was taken over by the Christians who converted it to a church dedicated to St George. North of the Forum, on the ruins of the thermae (baths) where tradition has it that St Demetrius was imprisoned and tortured, they built the Basilica of St Demetrius. Rebuilt in 412-13 by the eparch Leontius and enlarged in 629-34 according to a grandiose plan that included five naves, the church, despite having been ravaged by fire in 1917, remains one of the most notable monuments of the early Christian era.
Other churches of archaeological interest were built during the Byzantine period. These include the Basilica of the Virgin, called Acheiropoietos, after 448, St David's (late 5th or early 6th centuries), and particularly St Sophia (8th century), which is a harmonious blend of the Greek cross plan and a three-nave basilica plan. After the Latin conquest in 1205 it became the Cathedral of Thessalonika. When the city was returned to Byzantium in 1246, new churches were built, among which were St Panteleimon, the Holy Apostles, St Nicholas Orphanos, and the present St Catherine's.
When the Ottomans gained control of the city in 1430, most of the churches, new or old, were converted to mosques, and other Islamic sanctuaries were built (Hamza Bey Cami in 1467-68, Alaca Imaret in 1484). Under Ottoman rule (1430-1912), Thessalonika regained the status of major cosmopolitan city it had enjoyed during the early Christian era. This was particularly due to the arrival in 1492 of 20,000 Jews driven from Spain by the Edict of Alhambra. The multitude of cultural influences is reflected in the city's wealth of monuments, now sadly depleted, which were described by travellers such as Robert de Dreux (1665), Evliya Celebi (1668), Paul Lucas (1714), Félix de Beaujour (1797), and Abdul Mecid (1858).