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" When Constantine converted to Christianity, there basically was no Christian architecture. Local Christian communities met in converted houses, and especially in the face of periodic imperial persecution, the religion had developed no specific architectural forms of its own. In the fourth century, therefore, as imperial patronage and ongoing processes of conversion caused large numbers of specialist churches to be built for the first time, the religion took over an old form of public building from the Graeco-Roman world: the basilica. This was a rectangular, shallow-vaulted building, usually equipped with aisles around an elevated central nave and an apse at one end. It had long been used for town council buildings and audience chambers across the Mediterranean world, with the apse being occupied by the presiding figure of power (or indeed the emperor in the case of a palace audience chamber). For Christianity, the apse worked nicely for the sacred space of the altar, and the basilica was a building form essentially designed for meetings, which worked, too, as a space for church services "
― Peter Heather , Rome Resurgent: War and Empire in the Age of Justinian