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Deciphering
a Roman Blueprint
In the 1930s, hoping to energize Italy with memoties of its glorious past, Benito Mussolini ordered extensive and hasty archaeological excavations in Rome. Over the centuries, annual floods of the Tiber River had deposited soil all over the city. In particular, the mausoleum erected by Augustus around A.D. 30 to demostrate his power had acquired a layer of earth many metres deep outside its walls.
Digging through six or seven metres of it, the workers hit a pavement made of massive blocks of rock... When World War II started, the discovery was forgotten. But in the 1964 the Roman Service of Antiquities observed that chiseled into this pavement were full-size aechitectural plans for "a pediment and an inverted capital." The courtyard had apparently served as a workshop for an ancient building project. Used as a drawing board, the surface was inscibed with a series of designs of new monuments, so that the plans are superimposed in no descerrible order. In the 1980s my colleague Henner von Hesberg of the University of Cologne brought the grawings to my attention.
Not one but two of the incised outlines were of pediments, which crown the entrances to monuments, and von Hesberg hoped that from these I would be able to reconstruct a possible front porch that might have been built for the mausoleum. But when I sketched the drawings for myself, I became quite despondent. Neither of the pediments could be related to the mausoleum: they were simply too big. The topmost step at the mausoleum's entrance is about six metres wide. But the "elevation," or the architectural drawing as seen from the front, for the smaller pediments spans 17 metres. Intersecting with this drowing are curved lines of a Corinthian capital (which, placed on a column, would support a roof). The uppermost molding , or abacus, of this capital is 2,8 metres wide - far surpassing the abaci of most extant buildings. The second elevation is drawn using the same baseline as the first but on the opposite side.
The pitch of its triangular corner, at 24 degrees, is rather high: the Romans usually kept close to the Greek norm of anbout 14 degrees. THe fragment that is exposed shows the pediment to be at least 18 metres wide and probably much wider. The sheer size of the drawings makes it evident that they were laid out at full scale.
The workmen probably used them to build the structures they represent, measuring blocks of marble directly against their lines. Blueprints of this kind are known from the Temple of Apollo at Didyma (in modern Turkey) where they cover the unfinished inner walls. [...] A fine 17th-century example occurs in Rome itself. The plans for Francesco Borromini's bell towers -which once embellished the Pantheon but, reviled as "donkey's ears", were removed in the late 19th-century - are detailed on top of the cornice slabs encircling the pantheon's dome. But what monumental buildings did tha blueprints at the mausoleum's entrance describe? Trying to find a match seemed like hunting for the proverbial needle in a haystack.
No existing mearby structure was big enough. And looking at the wider cityscape, how many parts of ancient Rome were not once ornamented by pediments of imperial size? I do not believe in the oft-used procedure of trying to connect every new finding to the few structures known from classical times. Such results give a seem-ingly well-rounded impression but for the most part remain speculative. As it tourned out, my pessimism was misplaced. One thing was already clear at the time. Although ancient - as evinced by the six metres of earth under which they lay - the blueprints were from a time later than that of Augustus. The pavement abuts the staircase to the mausoleum, lying at the same level as the lowest vilible marble step. Brecause a stair is not normally built flush with the ground, I saw that the inscribed pavement. As the Tiber unendingly deposited its soil, the mausoleum must have aquired at least three pavements -the original one, still buried; the "drawing board", 1.7 metres above; and a third, of modern cobblestone, that was dug up in the 1930s. The inscribed courtyard has the same level as other pavements built in this area, Campo Marzio, around A.D. 100.
This clearly post-Augustan date raised another question. The mausoleum, surrounded by carefully designed parks and ornamented with obelisks celebrating the Divine Augustus, was a grandiose dynastic monument. If not Augustus as the patron of his tomb, who could have taken the liberty to use the area in front as a building yard? There can be no doubt that this was imperial property. One of the later emperors himself, or somebody with his consent, must have assigned it to the design office. That is where I left the problem in 1985. In the spring of 1992 I gave a seminar on the Pantheon, a temple that has been called the pinnacle of Roman architecture. One night that summer, as I walked home along a sylvan creek, my thoughts turned to the plans that had been gathering dust in my drawers. Nonsensical as it seemed, the designs certainly resembled the Pantheon's facade. "I should make a detailed comparison," I told my wife over dinner, "even if just for fun." But try as I might, I could not find an accurate drawing of the Pantheon's pediment. After some effort I located a measured drawing sketched in 1813 by the French architect Achille Leclère. But it did not list the measurements with sufficient precision, so I searched furter. Slowly, from a British volume of 1821, an American study of 1924 and a Danish work of 1968, I gleaned data on diversed aspects of the facade. When I finally pieced together the basic dimension, I was trilled. It showed an amazing match with the larger elevation.
The Danish study lists the unusually steep pitch of the pediment at "ca. 23 degrees"; the working drawing, we have noted, has 24 degrees. The consoles, or brackets, holding up the top and bottom cornices, as well as the height of a horizontal frieze, fit the blueprint to within one centrimetre. (The average distance between the consoles is about 82 centimetres; the elevation has 81 centimetres.) The distance between the massive columns average, from center to center, 4.52 metres; the drawing shows 4.51 metres. THe position of the two columns nearest the corner coincide with two circled marks in the elevation. Even a horizontal line where two rows of blocks meet is indicated in the working drawing. The plan was clearly used to construct the imposing facade of the Pantheon. The Pantheon was commisioned either by the emperor Trajan or his successor, Hadrian, who finished it around A.D. 120. (Of an earlier Pantheon at the same site, only some foundation blocks have been found so far.) Dedicated to Christianity in A.D. 609, the Pantheon remains a living temple, where thousands worship and Italy's great citizens -including the painter Raphael- are buried. The imperial building yard on which the Pantheon's block were sliced -the mausoleum's entrance- lies 800 metres from the Pantheon's site. This inconveniennt distance must have been offset by the presence of the Tiber River, along which the marble arrived by boat. The blocks were apparently offloaded, cut and then carted to the construction site.
Transporting rocks that weighed tons, it must also be said, posed little problem to Roman technology. The many obelisks that adorn Rome -single blocks of granite up to 33 metres high- came from Egypt. The Pantheon is ornamented with precious and colorful stones that came from distant corners of the empire and even from a catalogue of its extent. In addition to the logistics of Roman architecture, the elevation reveals its aesthetics. The three elementary dimensions of the Pantheon's facade -diameter of the columns (1.495 metres plus or minus two centimetres); "clear distance," or space between the columns (3.02 metres); and height of the columns (14.14 metres plus or minus one centimetre)- are in the ratio of 1 to 2 to 9.5. This formula is among those described by Hermogenes, one of the most celebrated architects of the Hellenistic age, as belonging to an ideal facade. (His ideas are brought to us by Vitruvius, the engineer and Theoretician from the first century B.C.) For the first time in the exploration of Roman architecture, a numerical recipe for beauty, as known from textual source, can be tied to an existing monument. Each time they visit the Mausoleum of Augustus, tourists and scholars trample on this record of the Pantheon's exquisite proportions.
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