When the “Peace of the Church” had been proclaimed by Constantine and Christians were able to worship openly, the age of church-building commenced, the Emperor himself setting a lead. After the edict of Theodosius, making Christianity the State religion, many of the pagan temples were adapted to the purposes of the Christian ritual, or their columns and decorative features were appropriated for the building of new churches. The former practice accounts for the preservation of the Parthenon, Erechtheion, and the Temple of Theseus at Athens. An instance of the method of conversion is to be traced in the =Cathedral of Syracuse, Sicily=, which occupies the site of an ancient temple. Walls were built between the Doric columns of the peristyle, while the walls of the cella were pierced so as to communicate with the peristyle, which thus served as aisles. Another instance is that of a temple in =Aphrodisias=, in Caria, Asia Minor, where the walls of the cella were entirely removed, and walls were built outside the peristyle to form aisles, while to increase the length of the nave the front and rear portico columns were set in line with the others. =Basilican Plan.=--These changes coincided with the general adoption of the basilica plan in the case of new buildings. For the early Christian churches show very little regard for the appearance of the exterior. Attention was concentrated on the interior, in fitting it for ritual worship and in beautifying it, and to both these objects the basilica plan most readily contributed. The earliest example in Rome of a church so planned is that of =St. John Lateran=, which, however, has been completely remodelled by subsequent additions. The next in point of time was the =Cathedral Church of St. Peter=, erected near the spot in which the saint was martyred in the circus of Nero. It was torn down in 1506 to make room for the present cathedral commenced by Julius II; but the appearance of its principal façade is known from Raphael’s mural painting “Incendio del Borgo,” in the stanze of the Vatican, and there is a record of its plan. The latter shows that the basilica building was approached by an atrium, surrounded by either colonnades or arcades, enclosing a rectangular space, open to the sky and having a fountain in the centre. With the water the worshippers sprinkled themselves, a symbol of purification still preserved in the “holy-water” vessel, placed inside the entrance of Roman Catholic churches.