The main difference between contemporary meeting rooms and Christian basilicas is due to liturgical needs influencing internal layout rather than to architectural technique. Yet here too the variety of local customs meant the absence of a single type of layout. 1. The position of the altar. The main element of a church intended for community meetings for the eucharistic synaxis was the altar which was of course inside the building, while the pagan altar of sacrifice was in front of the temple, but altars very soon appeared also in cemeterial churches or churches dedicated to a martyr.
Alternatively, the custom of placing the relics of one or more saints in or near the altar of an urban basilica also spread quickly, particularly in Africa. This deposition of relics became an essential element, no doubt at first the only element, of the dedication of churches, which explains why the patronage of saints replaced more neutral designations: ecclesia or basilica or sometimes an adjective taken from the builder’s name. In a church devoted to the cult of a martyr, the altar was linked with the position of the tomb or cenotaph, whose vicinity was sought sometimes by supposition, as in the Vatican basilica. In an urban basilica, the position was in principle freer and depended on the desired relationship between clergy and congregation.
We observe great regional variety and, contrary to what was held at the time of the liturgical reforms of Vatican II, the usage of the early Christian period can provide no rule either for layout or for orientation, since in one and the same region we note that the priest sometimes turned his back on the congregation and sometimes faced them, at least in the few cases where his position is confirmed by sure material evidence.