The first questions which present themselves to us are these. Why was the particular site on the Vatican Hill chosen by the emperor for his church? And did a previous building associated with St Peter exist upon it? These questions, which have been examined and thrashed out by many eminent past and present-day scholars with the most scrupulous attention, I shall endeavour to summarize. For a start, let us consider the history of the site in ancient times.
The Mons Vaticanus, or Vatican Hill, derives its name from the worship of Cybele, whose fertility rites associated with her youthful lover Attis were performed here, ex vaticinatione archigalli - that is to say in accordance with the prophecies of the goddess' high priest. On this hill of prophecy the annual spring festival was held. A pine tree, the phallic symbol of Attis, was reared outside the temple in preparation for the Day of Blood. The events that took place on this occasion were to commemorate the self-castration of the youth at the instance of Cybele, whose motives were to prevent him marrying another. In Asia Minor, whence the Cybele cult was brought to Rome, Attis was called Papas, or Zeus Papas. By certain ancient writers his myth has been confused with that of Apollo and, like the great god of perennial youth and beauty, he was supposed to have been slaughtered by a wild boar. But Attis was rather a god of vegetation and propagation, and the spring festival coincided with his death and resurrection. The hill to which the worshippers resorted at the festivals being outside the city walls was indeed until medieval times at the mercy of enemy assaults. This was a cogent reason why the earliest popes preferred not to reside in the Vatican but in the comparative safety of the Lateran Palace. The elder Pliny clearly thought the hill a barren and unattractive spot. He referred to it as infamis Vaticanis locis, an area infested with mosquitoes, which in the summer of 69 decimated the troops of Vitellius posted there. Few people lived on it apart from some fabricators of cooking utensils and wine jars. Worse still, the hill produced a horrible wine. 'If you drink Vatican wine', wrote the satirist poet Martial, 'you are drinking poison: if you like vinegar you will like Vatican wine: Vatican wine is perfidious.' From time to time members of the imperial family attempted to improve the soil. Agrippina senior, Nero's grandmother, drained it, digging channels to take the water down the sticky clay slopes, altering the contours and constructing terraced gardens, and even a covered way to the Tiber. When Nero inherited or appropriated the gardens after murdering his mother, Agrippina junior, in A.D. 59 they were flourishing. He built a bridge over the river near where the Santo Spirito hospital now stands. So whenever he wished to dally in his grandmother's pleasances or to disport himself in the circus which his predecessor Caligula had made on the lower ground, he could go there at a moment's notice