The history of ecclesiastical architecture cannot be clearly understood without going back to the beginning. The original type of all Christian churches is universally acknowledged to have been the Roman Basilica. The Latin word derives from the greek "(tribunal of the king.") These buildings were numerous in all parts of the empire, and were the most convenient structures then existing for the purpose of congregational worship. Their original use was for the law courts, the merchants’ exchange, and market halls, no place being entitled to municipal privileges which did not possess one. The oldest known basilica, the Basilica Porcia, was built in Rome in 184 BC by Cato the Elder and destroyed by a fire in 52 BC.
Basilica of Maxentius, Forum, Rome 308-312
We do not find any notice of their having been converted into churches in Eusebius or the other ecclesiastical historians of the period, though it is constantly asserted by modern writers. It is, however, clear that they served as models for the churches. Many of them are said to have been consecrated by Pope Sylvester in the time of the Emperor Constantine, and they became one type of the earliest Christian churches. Their plan was uniform, consisting of a parallelogram divided into three parts longitudinally by two rows of pillars. These divisions became the nave and aisles of the church. The aisles usually had galleries over them: at one end was the tribune for the judges, arranged in a semicircle This became the apse of the church, and the place for the priests behind the altar, the entrance being at the opposite end. Putting an altar instead of the throne made a church.
In a few instances they were double, having a tribune at each end, and the entrances at the sides. For some centuries the type of the basilica appears to have been generally followed, but in process of time various changes were introduced; one of the first was to place a transept across, thus producing a cruciform plan. In the western parts of the empire, the plan was that of the Latin cross, the nave being long, the choir and transepts short; in the eastern parts, the plan generally adopted was the Greek cross, the four arms being of equal length. It is natural to suppose, also, that in different parts of the Roman empire the character and style of building, the more or less perfect masonry or brickwork, would vary according to the civilization of the different provinces and the nature of the building materials, and this we find to have been the case.
The Church of the Nativity , Bethlehem, is considered to be the oldest continuously operating Christian basilica in the world. The present church was built by Emperor Justinian in 565 AD (photographed by Lewis Larsson; wikimedia)
In Italy itself the plan of the basilica was in general closely adhered to: the original basilicas which served as models were numerous in that country, and the ruins of the pagan temples, the palaces and public baths of the ancient Romans, which were destroyed, furnished in many instances the materials of the new churches, the original columns, capitals, entablatures, and other finished parts being employed again, while the main structure was wholly of brick, carefully concealed within by plaster and ornament. In the earlier examples the columns carried horizontal entablatures only, afterwards small brick arches were introduced »
Basilica of San Vitale, Ravenna. The church has an octagonal plan and not a typical architectural basilica form. 6th c.
These were at first concealed behind the entablature, but by degrees the entablature was abandoned and the arches were shewn. On the exterior the brick walls were sometimes cased with slabs of marble. Circular churches were occasionally used from an early period, as St. Vitale at Ravenna, and St. Stefano Rotondo at Rome. In Greece, on the other hand, the models before the eyes of the people were superior to those of Rome itself, and as Byzantium became the centre of civilization, the art of buildiflg also was in higher perfection there than in the other provinces. The ground plan was accommodated to the opinions of the people, the Greek cross of four arms of equal length being invariably adopted. Advantage was taken of the facilities afforded by this ground-plan, and of the skill of the workmen, to erect those beautiful cupolas which are still the admiration of the world for their scientific and skilful construction. The Byzantine style thus formed was introduced in the course of time into several other provinces. In Italy it is rare, but a few specimens are found: in the south of France it is more frequent; in the province of Perigord, churches of a thoroughly Byzantine type are numerous.
Saint Front Cathedral, Perigueux, France was designed after the Saint-Marc basilica in Venice
In Lombardy a distinct style was formed, which partakes in some degree of the Byzantine character, but is readily distinguished from it by the absence of the cupola. In the republic of Pisa another peculiar style was introduced in the eleventh and twelfth centuries, distinguished chiefly by the great number of small columns used on the exterior. The best examples of this style are at Pisa and Lucca: the well-known falling tower of Pisa is one. In the countries bordering on the Rhine a similar style prevailed, and it continued in use down to the thirteenth century. Many Romanesque churches in Italy and on the Rhine are contemporary with our cathedrals at Lincoln, Wells, and Salisbury.
Basilica si Santa Maria della Salute, Venice
The dome of the basilica inspired artists like Canaletto, J. M. W. Turner, John Singer Sargent, Francesco Guardi.