The large number of churches in Rome.--The six classes of the earliest of these.--I. Private oratories.--The houses of Pudens and Prisca.--The evolution of the church from the private house.--II. Scholæ.--The memorial services and banquets of the pagans.--Two extant specimens of early Christian scholæ.--That in the Cemetery of Callixtus.--III. Oratories and churches built over the tombs of martyrs and confessors.--How they came to be built.--These the originals of the greatest sanctuaries of modern Rome.--S. Peter's.--The origin of the church.--The question of S. Peter's residence and execution in Rome.--The place of his execution and burial.--The remarkable discovery of graves under the _baldacchino_ of Urban VIII.--The basilica erected by Constantine.--Some of its monuments.--The chair and statue of S. Peter.--The destruction of the old basilica and the building of the new.--The vast dimensions of the latter.--Is S. Peter's body really still under the church?--The basilica of S. Paul's outside the walls.--The obstacles to its construction.--The fortified settlement of Johannipolis which grew up around it.--The grave of S. Paul.--IV. Houses of confessors and martyrs.--The discoveries of padre Germano on the Cælian.--The house of the martyrs John and Paul.--V. Pagan monuments converted into churches.--Every pagan building capable of holding a congregation was thus transformed at one time or another.--Examples of these in and near the Coliseum.--VI. Memorials of historical events.--The chapel erected to commemorate the victory of Constantine over Maxentius.--That of Santa Croce a Monte Mario. Rome, according to an old saying, contains as many churches as there are days in the year. This statement is too modest; the "great catalogue" published by cardinal Mai[60] mentions over a thousand places of worship, while nine hundred and eighteen are registered in Professor Armellini's "Chiese di Roma." A great many have disappeared since the first institution, and are known only from ruins, or inscriptions and chronicles. Others have been disfigured by "restorations." Without denying the fact that our sacred buildings excel in quantity rather than quality, there is no doubt that as a whole they form the best artistic and historic collection in the world. Every age, from the apostolic to the present, every school, every style has its representatives in the churches of Rome.