The Founding of St. Peter’s Basilica

The Italian astrologer Gaurico in his Tractatus published the electional chart for the foundation of the modern St. Peter’s Basilica in Vatican City. Pope Julius II asked his astrologers to elect an auspicious time to begin construction. The papal astrologers determined that a favorable date and time would be April 18, 1506 (Julian calendar) at about 9:21 AM.

An internet search revealed the following facts:

The latitude of St. Peter’s Basilica, Rome, Vatican City is 41.902168, and the longitude is 12.453937.
St. Peter’s Basilica is located at Vatican City, Rome, Italy, with GPS coordinates of 41° 54′ 7.8048” N and 12° 27′ 14.1732” E.

At this location on the Vatican Hill and on the other side of the Tiber River, in 318 AD the Emperor Constantine decided to build a large Basilica in honor of the Apostle St. Peter, known as the Constantinian Basilica . Construction began between 319 and 322, was consecrated in 326 AD and completed around 349 AD.

The current Basilica  is an Italian Renaissance and Baroque church, initially planned in the 15th century by Pope Nicholas V and then Pope Julius II to replace the Old St. Peter’s Basilica, which was built in the fourth century by Roman emperor Constantine the Great.

Here is the electional chart of the foundation of St. Peter’s Basilica from Gaurico’s text:

This chart uses the older Julian Calendar.
Latin Text:
Stellae insalubres cum nodo Austrino dispendia intolerabilia denuntiabant, & inferent ad calcem usque Virginiei partus 1571. vel iam tandem ad 1608.uti colligitur ex directione horoscopi ad Jovem & postremo culmigantis coeli ad trigonicam Jovis radiationem.
Rough translation: The infortunes [Mars & Saturn] and the South Node [being in the 2nd house] portend intolerable expenses, and they will bring the construction to a heel until the delivery of Jupiter to the Ascendant by primary motion in 1571, or finally in 1608 as can be gathered from the trigonic direction of Jupiter to the midheaven

Gaurico does not comment on why the Roman Catholic Church astrologers selected this chart. Cancer rises, perhaps symbolizing the church as an archetypal mother. The MC and the Ascendant-ruler Moon lie in Pisces (associated with Christ and the Christian era, Pisces being the Fish, and Christ being the fisher of men). The Moon also occupies the 9th house of God, religion and eccesiastical matters. The Moon favorably aspects the Sun, the Part of Fortune, and the Ascendant. The troublesome planets, Mars and Saturn, are placed in the 2nd house in aversion to the Ascendant, the Moon, Sun, Jupiter, and the MC so that they are not aspectually connected. The lesser benefic Venus is in whole sign trine to the malefics in the 2nd and is received by Mars. The Sun applies to square the malefics in Leo, so that the Sun receives both Mars and Saturn. No doubt Pope Julius II’s astrologers would have taken these factors into account.

A modern rendering of this chart from Solar Fire software has slightly different, and presumably more accurate, positional values for the planets because in 1506 the telescope had not yet been invented:

A modern approximation of the chart published by Gaurico. The planatary positions are a bit different, and the MC has a R.A. of 355:29 instead of R.A. 355:25 used by Gaurico to achieve an Ascendant of 16:00 Cancer at the site of construction of the Basilica.

Gaurico notes that the troublesome planets and Lunar South Node in the 2nd house indicates great expenses and delays in the construction. These problems will be surmounted by the benefic Jupiter when it reaches the eastern horison by primary driection in 65 years (in 1571), at which time the primary directed ASC will be at 7 Virgo, or else when Jupiter sextiles the directed MC in 102 years (in 1608), at which time the primary directed MC will be at 7 Cancer. at the midpoint of the Sun-Jupiter trine.

Gaurico appears to be quickly calculating the primary directed chart angles, doing simple arithmentic and looking in a table of houses.

In 1571, 65 years will have passed. Ptolemy advances the MC symbolically at a rate of one degree per year, and one degree passes over the MC about every 4 minutes on the clock. Thus, 65 years x 4 min/year = 260 minutes, so that 260 minutes after the time of the original chart, the MC will be at 2 Gem 44 and the directed Asc will be at 7 Vir 03.

Similarly, in 1608, 102 years will have passed since the founding, and 102 years x 4 min/year = 408 minutes, so that 408 minutes after the time of the original chart, the MC will be at 7 Vir 08 in sextile to both natal Jupiter and natal Sun.

The center chart is the foundational chart for St. Peter’s Basilica.
The middle chart shows the original Angles advanced by primary direction by 260 minutes to the year 1571.
The outer chart shows the original Angles advanced by primary direction by 408 minutes to the year 1608.

Addendum: 28 Sep 2024

Commenting about this chart on his Facebook site, astrologer Giovanni Londoño Romero writes:

“En esta carta, cuatro estrellas fijas en conjunción cerrada con cuatro elementos claves dentro de la carta, resultan especialmente significativas: Pollus con Ascendente, Achernar con Luna, Almach con Sol y Difda con MC.
Cuánto más pienso en ello, más me convenzo de que el inicio de la construcción de la Basílica de San Pedro no fue fruto de la casualidad, sino del profundo conocimiento astrológico. Cada una de esas cuatro estrellas jugó un papel crucial en la consolidación del cristianismo en el mundo del siglo XVI y su posterior evolución hasta nuestros días.”

[In this chart, four fixed stars in close conjunction with four key elements within the chart are especially significant: Pollus with the Ascendant, Achernar with the Moon, Almach with the Sun and Difda with the MC.
The more I think about it, the more I am convinced that the beginning of the construction of St. Peter’s Basilica was not the result of chance, but of profound astrological knowledge. Each of these four stars played a crucial role in the consolidation of Christianity in the world of the 16th century and its subsequent evolution up to the present day.]