THIS BOOK had its beginnings many years ago in the excavations below St. Peter's. Standing beside one of the Roman tomb buildings that had been filled in and then covered over by the floor of Constantine's basilica, I could look up through a modern ventilator into the nave of the vast Renaissance St. Peter's that replaced Constantine's shrine for the apostle. Pagan antiquity and medieval Christianity were around me just as much as was their Renaissance successor. Constantine the Great set these changes in motion, but the Constantinian moment in Rome was brief, hardly more than thirteen years between 312 and 326. In fact it was even shorter because in 326 Constantine returned to a capital that he had not seen for a decade. And his sights were already set on Constantinople, the new Rome on the straits between Europe and Asia where he was about to establish his new capital. Yet the cityscape of Rome of 326 was not that of Rome of 312. It was significantly Christian, but it was also overwhelmingly pagan. And in this way it mirrored, I have come to believe, the personality of its ruler. Constantine was a Roman emperor and continued to carry out the civic and religious duties of the pagan emperor. He was the patron of the Christians but exercised his patronship from an exalted position in respect to the ministers of the church, a position which, as a divinized ruler, he maintained even in respect to the Christian God. Yet Constantine had prepared for death in a tomb of imperial dignity on the Via Labicana in the company of two Christian martyrs and with provision for a following of the faithful beneath the roof of the apse-ended hall attached to the imperial mausoleum. This complex and the group of other apse-ended basilicas which were built in the cemeteries along the roads leading south and east from the city are the most (p.x) notable architectural innovations of Constantine's Rome, even more than that first great cathedral of Christendom and church of the bishop of Rome, San Giovanni in Laterano.
The planning and writing of this book took place during a sabbatical leave from teaching duties in 2001–02. Part of that time was spent as a Visiting Scholar at the American Academy in Rome, where I enjoyed the advantages not only of that great institution but also of the numerous resources of the city, while during my time in Providence I relied on the unsurpassed resources of the Brown University Library. I am particularly indebted to the Photographische Abteilung of the German Archaeological Institute and to Dr. Sylvia Duebner, its director, and to Dr. Katrin Stump for access to resources on which I have drawn heavily for illustrations. A similar debt is owed to the Fototeca Unione presso l'Accademia Americana and to Dr. Lavinia Ciuffa. The Ernest Nash archive at the Seminar für Griechische und Römische Geschichte and Dr. Margarita C. Lahusen have made it possible for me to illustrate Dr. Nash's portrait of Pope Pius XII. Dr. Olof Brandt has favored me with permission to reproduce his reconstruction drawing of the Lateran Baptistry, and Dr. Archer Martin arranged for reproduction of the plan of the newly discovered Christian basilica at Ostia. The map and figures 4.7, 4.17, 4.23 illustrating the Tomb of St. Peter have been drawn with care and skill by Ms. Alice Walsh. The Brown University Library made a special reproduction of the engraving of Etienne du Perac, fig. 1.3. Mr. Harry Haskell took an early interest in my work on Constantine and encouraged the presentation of the resulting manuscript to Yale University Press. It has been a pleasure to have Mr. Lawrence Kenney as my editor. Names of buildings and places are given in what I consider to be the most familiar form of each, Italian, English, or Latin. All dates not otherwise specified are A.D.
The most powerful tool for dating Roman construction is the brick stamps which at various periods, including that of the tetrarchy, were applied before firing and frequently dated by the consuls of the year. The second tool, of more importance in studying buildings of the Constantinian period, is the height of the courses of brick facing on concrete walls. In giving dates based on the latter criterion I have not exercised my own judgment but have accepted the opinions of scholars dealing directly with the monuments in question.
Debts to friends are many. But it is a particular joy to record the help of some of my oldest Roman friends. Prof. Silvio Panciera and Prof. Mara Panciera Bonfioli encouraged my uncertain steps on the borders of the late antique and undertook to read the first draft of the manuscript. Dr. Giuseppe Sicari and Prof. Mariella Sicari Montana kept me abreast of the ever-surprising world of archaeological exhibitions in Italy, which for Christian Rome culminated in the frenetic activity of the Jubilee Year 2000. Prof. Stefania Quilici Gigli invited me to illustrate my views on Constantine's Rome in two lectures at the Seconda Università di Napoli, Santa Maria di Capua Vetere. At the Fabbrica di S. Pietro in Vaticano I was received with great courtesy by Dr. Alfredo Maria Pergolizzi. I made one new friend during the course of writing whom I wish I had known in life but whose spirit I have grown to treasure. This is (p.xi) Richard Krautheimer. It is not only the monumental achievement of the Corpus basilicarum christianarum romae, the flesh and blood of the third chapter of this book, that has made Krautheimer my guide and friend. It is his good sense and his humor, which on more than one occasion during the course of this work made me feel that I was listening to his voice more than reading his prose. And finally, a word must be said in memory of the departed vice prefect of the Apostolic Vatican Library, who introduced me to the complexities of Christian archaeology. Mgn. José Ruysschaert would not have agreed with the conclusions I have reached concerning the explorations below the confessional of St. Peter's, but he would have listened and smiled as he replied. My wife has played her now oft-repeated role of muse. (p.xii)