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Italy, Rome, St. Peter's Basilica |Description
Professor Dale Kinney

St. Peter's was built on the slope of the Vatican Hill (Mons Vaticanus), in a cemetery which had grown up around the ruins of the Circus of Nero. Legend had it that Peter was martyred with other Christians in this circus in 64, in retribution for the famous fire that burned much of Rome. By the third century CE, a modest tomb below a wall in the cemetery was venerated by Christians as Peter's.

The huge basilica constructed in the fourth century obliterated much of the cemetery, leaving only the wall marking Peter's grave.

Italy, Rome, Circus of Caligula and Nero
, model

Italy, Rome, Old St. Peter's, plan (Krautheimer)

Italy, Rome, Old St. Peter's, reconstruction of longitudinal cross-section (Arbeiter, 1988)
The fragmentary remains of Peter's grave were encased in copper and a shrine above it became the focal point of the new building, standing just in front of the apse. The apse pointed west, so that the rising sun would shine in through the doors at the east (later churches would reverse this orientation). Because of its size the basilica had four aisles rather than the usual two, and it was made still larger by inserting a transverse space (the transept) between the nave and the apse.

Italy, Rome, Old St. Peters, plan of west end showing
transept located between nave and apse (Jongkees, 1966)

The total length of St. Peter's from entrance to apse was about 123 m. (403 1/2 ft.); the nave alone was as long as an American football field (298 ft.). The combined width of nave and aisles was about 63.4 m. (208 ft.). The colonnades separating the five parallel spaces of nave and aisles had 22 columns each, for a total of 88 columns; there were also two columns at the end of each aisle (4 X 2 = 8) and two more at each end of the transept, to make the total of 100 columns for which St. Peter's was famous as we know from Gregory of Tours.

The nave elevation was like that of the Lateran cathedral, with a colonnade supporting a tall wall pierced by large windows; a similar elevation appeared between the aisles.

Italy, Rome, Old St. Peter's, Reconstructed cross-section (Bannister)

Italy, Rome, San Giovanni in Laterano,Basilica
, Reconstruction

Italy, Rome, Old St. Peter's (right) compared to Chârtres Cathedral
The height of the nave from the pavement to the peak of the roof was nearly 38 m. (124 1/2 ft.), taller than the nave of Chartres Cathedral.

Compare the plan of Old St. Peter's with the Romanesque Cathedral in Durham located in northern England.

From the pavement to the horizontal roof beams the height was about 104 ft., with a ratio of colonnade to wall of 2:3 (in other words, the colonnade with its entablature rose to 43 ft., and the wall rose 61 ft. above that). To be supported by columns with the open spaces between them, the wall had to be very thin (.92 m., less than 3 ft.).

Italy, Rome, Old St. Peters, nave wall, drawing by Grimaldi

Italy, Rome, Old St. Peter's, drawing by Grimaldi, c. 1608

This was a daring construction, contrary to normal Roman practice (which favored extra-thick walls) and to basic concepts of engineering. The Renaissance architect Leon Battista Alberti severely criticized the design around the middle of the fifteenth century, when he found the upper walls leaning out of plumb; but by then they were already 1100 years old.

Windows in the outer aisle walls filtered light into the nave, but the principal natural illumination came from the nave clerestory: eleven windows on each side, piercing the wall above the colonnade. Theoretically eleven windows could have been aligned with alternate intercolumniations [with 22 columns, there were 23 intercolumniations], but it is not certain that this was so. If not, fenestration and colonnades followed two slightly different rhythms in the nave. There were also a number of windows in the walls of the transept.

The reconstruction of ceilings and roofs remains uncertain. Two texts from around 400 use the term lacunar, which means coffered ceiling, with reference to the transept (and nave?), but if such a ceiling existed it was forgotten by the later middle ages. The south-north section made around 1608 by Grimaldi shows open timber roofs over the nave and aisles.

If such a roof was visible originally, its beams would have been gilded. Since the span of the nave was more than 87 ft. (ca. 23.6 m.), those beams there were enormous. Pope Honorius I had to replace 16 of them in the seventh century, and the new beams were gilded as well. The same pope received permission from the emperor to take bronze roof tiles from the Temple of Venus and Rome in the Roman Forum to put on the roof of St. Peter's. Over the aisles, the 17th-century section shows a single continuous roof; if this is accepted as the original arrangement, one has to explain the purpose of the semi-circular openings in the inner aisle walls. For this reason some scholars prefer to reconstruct a stepped profile, with the roof over the outer aisles about 18 ft. lower than the one over the inner aisles, and the openings functioning as windows between them.

The height of the transept also is not known for certain; many scholars believe that it was not as tall as the nave.

Italy, Rome, Old. St. Peters, alternative reconstruction of transept height (Arbeiter, 1988)

Italy, Rome, Old St. Peter's, reconstruction showing the transept height lower than the nave (Christern and Thiersch, 1969)
Fifty years after St. Peter's was built, the designers of St. Paul's basilica [link to related images, St. Pauls, would make the transept higher and broader, so that the cruciform silhouette was more emphatic; but the cross-shape was latent in the transept from the start, and symbolism was likely one of the motivating factors behind the invention of the transept at St. Peter's.

All of the columns in Old St. Peter's were spoils (spolia), that is, elements made for earlier buildings, and reused. Reuse of architectural ornament was a widespread practice in Rome by the end of the third century, when a dramatic collapse of the industrial and transportation infrastructure made it impossible produce new elements and ship them to Rome from the quarries. Like the Arch of Constantine, decorated with reliefs taken from various second-century monuments, Constantine's basilicas all were built with reused columns and capitals.

Those in St. Peter's were unusual in the diversity of their materials, and therefore of color. Sixteenth-century records indicate that the column shafts in the nave colonnades were of at least 5 different materials: red granite (from Aswan, in Upper Egypt); gray granite (also from Egypt); cipollino, a green-veined marble from Greece; portasanta, a mottled, reddish marble from the island of Chios; and africano, another mixed-color (red, black, white) marble from the coast of modern Turkey.

Samples of marble showing the variety of colors and textures available in the ancient world, from Enciclopedia dell'arte antica, III, Rome 1995
These stones were all very expensive in the fourth century, and their use reflects an aesthetic preference for color and precious materials. Coloristic diversity, opulence of materials, and gleaming, polished surfaces were essential elements of the architecture of St. Peter's and of all high-status public buildings in late antiquity and the early Christian period. These qualities were still valued a millennium later. The Renaissance Pope Paul II (1464–1471) is reported to have said that two of St. Peter's columns were worth "more than the whole city of Venice".

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