The catacombs lie for the most part within a three mile radius of the wall of Aurelian. They number forty-five, and it is calculated that the passages, galleries, and chambers of which they consist cover several hundred miles, forming a vast underground city--"subterranean Rome." For the first 300 years, until "the Peace of the Church," this was the ordinary place of burial, certain catacombs being affiliated, from the third century, to the ecclesiastical regions in the city. Even after the "Peace" Christians were sometimes buried here, until the fifth century, after which the catacombs were visited as places of pilgrimage for another 400 years. From the ninth century they fell into complete neglect; no one visited these sanctuaries of the sufferings, these monuments of the human affections and religious beliefs of the first Christians. Visitors heard that Rome was built upon terrible underground chasms, filled with snakes, some part of which was every now and then revealed to the terrified inhabitants. No one penetrated till the fifteenth century--the first pioneer belongs to the sixteenth--and it was not till the second half of the nineteenth that a new world was laid bare to the student by the excavations of De Rossi, who rediscovered the great cemetery of Callistus, containing the now famous "papal crypt," and whose labours have resulted in restoring to us nearly twenty catacombs. The terrible underground chasms filled with snakes were found to be galleries of tombs, crypts of all sizes, lighted by shafts, some with seats for catechists, some adapted as miniature basilicas, decorated with frescoes recording biblical scenes, New Testament parables and symbolical representations of New Testament events--(in which the "apocrypha" is not distinguished from the "canon," and the history of Susanna and the Elders sustained the faith and comforted the courage of Christians by the side of the scene of Moses striking the rock or Christ feeding His disciples); eloquent with inscriptions in the epigraphy of the first four centuries, recorded in moments of simple human emotion, intended only for the dead and those who survived them sorrowing; and lastly, covered with _graffiti_, with prayers, names, acclamations, scratched on the walls of galleries leading to some favourite crypt by pilgrim visitors in later centuries. [Illustration: FLAVIAN BASILICA ON THE PALATINE See pages 31, 35, 45, and fly-leaf, page 252.] In this hidden and quiet place of the dead there is recorded a revolution parallel to a volcanic upheaval of nature. Here we have a permanent record of the meeting of classical Rome with Judaea and Christianity; here the graceful art of Pompeii meets the imagery of the Hebrew bible; here the Flavii met the Jews of the Dispersion; here as in a Titanic workshop, Rome, taking its religion from the Jew, moulded the faith which the Chosen People had discarded into the greatest religious organisation on earth--Catholic Christianity.