In the 4th century, once the Imperial authorities had decriminalised Christianity with the 313 Edict of Milan, and with the activities of Constantine the Great and his mother Helena, Christians were prepared to build larger and more handsome edifices for worship than the furtive meeting-places (such as the Cenacle, cave-churches, house churches such as that of the martyrs John and Paul) they had been using. Architectural formulas for temples were unsuitable due to their pagan associations, and because pagan cult ceremonies and sacrifices occurred outdoors under the open sky in the sight of the gods, with the temple, housing the cult figures and the treasury, as a backdrop. The usable model at hand, when Constantine wanted to memorialise his imperial piety, was the familiar conventional architecture of the basilicas.