which was originally located a separate baptistery. Surviving from both large basilican halls are rich mosaic pavements showing (amongst other scenes) Jonah and the Whale, and a series of, mainly female, donor portraits. It appears that similar cathedrals of double-basilica and baptistry were soon afterwards erected in Milan, Trier and Pavia; but that subsequently single-basilican churches became the more common cathedral model. Constantine's declaration of imperial favour towards Christianity transformed all aspects of Christian life in the Roman Empire. From being a minority religion, largely confined to urban areas and restricted social groupings, and subject to official hostility and occasional persecution; Christianity acquired greatly expanded numbers of potential adherents of all classes, initially still within city areas, but eventually extending out to the pagus, the city's rural hinterland. The consequence was a radical expansion in the buildings, funding and personnel of associated Church establishments throughout the 4th century. The first cathedrals represent this expansion in material form. Buildings The location and layout of the first cathedrals varied substantially from city to city, although most, as at Aquileia, tended to be sited within the city walls but away from the urban centre; certain elements are almost always found. Basilicas Basilican halls had previously been characteristic of major civic complexes and military headquarters buildings; but now became the standard structure for accommodating large Christian congregations. From now on, the term basilica denotes any substantial church building. These new basilicas were wholly different in scale from earlier Christian assembly halls, as they were also different in form from any Roman non-Christian temple or religious structure. The halls were longitudinal, aisled, and flooded with light from large clerestory windows. Floors and walls were richly decorated with mosaic and inlay – usually in abstract or floral patterns. The two original double basilicas at Aquileia had both been about 37m by 17m in size, but within 30 years one hall was quadrupled to 73m by 31m. This expanded basilica now demonstrated three additional features that became characteristic of early cathedrals: an enclosure at the eastern end of the church surrounding the altar; a east of the altar facing west, and consisting of a raised dais with a centrally place bishop's throne and benches either side for the clergy of his familia; and a partitioned-off narthex at the western end into which catechumens would withdraw during the central act of the Eucharistic liturgy. Baptisteries The baptistery in