Abstract

St. Peter's Basilica is a familiar cultural landmark, begun under the patronage of Pope Julius II by the architect Donate Bramante and substantially completed by Michelangelo. Following a common Renaissance practice, a horoscope was produced for the foundation ceremony of the great structure. It suggests several features of Renaissance astrological practice in coordinating the heavens with the earth. This essay argues that the horoscope published in 1552 is not the original horoscope but, rather, a "rectified" chart made after the church construction had been stalled for nearly forty years; that the date had been chosen according to religious and political dictates, and so the astrologer had to work with the planetary positions that pertained on 18 April 1506; that the astrologer chose the time of day-a time correctly noted not in the published horoscope but in the diary of Julius's personal secretary-because it coordinated the founding of the basilica with the important horoscopes of its patron and its region; that the primary patron of the basilica was not Julius but, rather, Christ, whose geniture was discussed in astrological texts of this era; that the coordination of the basilica's horoscope with that of Christ simultaneously coordinated the great structure with the thema mundi, the horoscope for the birth of the world; and that several putative horoscopes for Julius II seem related to those of the basilica and of Christ