In general the altar was rarely, as it has been in Western churches until recently, in the apse, which usually accommodated the clergy, whence the name presbyterium see below. The only exceptions are represented by small chapels and by two or three regions: NW Syria, where the altar was often in the raised apse, sometimes against the back wall; Spain, where the altar was situated, at least in the 5th c., at the center of the apse, which was generally not raised; and sometimes Dalmatia. The most frequent position, esp. in the Aegean, the Balkans, Syria, Palestine and Italy, was in line with the apse or slightly forward of it, on a podium, at the same level as the apse or in a small enclosure connected to it.
In N Africa and sometimes in the N Adriatic, the altar could be in the middle of the nave in an enclosure which was either separate or connected to the apse by a corridor, but in time we notice in Africa a tendency to bring it closer to the apse, as in the previous type. 2. The form of the altar and the ciborium. It is quite clear that the Christian altar is directly derived from the Roman dining table. Its appearance is often so similar that it is difficult to distinguish them in museums and archaeological repositories without a sure place of origin or specific sign and inscription. The most common form was the rectangular marble slab with molded margins thus the surface was not flat, nearly always resting on four feet, sometimes more in the case of large tables, at an average height of one meter. But other forms were also used, like those adopted in late dining rooms where couches were arranged in a semicircle: the semicircular or circular form. This form has wrongly been named Coptic, because the first examples found were still in use in the churches of Egypt. Examples have now been found throughout the Mediterranean.