Soprintendenza Archeologica di Roma
Piazza Santa Maria Nova, 53
00186 Rome, Italy
Fax: +39-06-67 87 689
Over the last fifteen years, publications, archaeological excavations and restoration work have changed our traditional view of the Pantheon. Under the direction of Paola Virgili, the Rome Town Council Archaeology Office has recently excavated the piazza where the Pantheon is situated and the State Office for Monuments has begun restoration of the rotunda, under the direction of Mario Lolli Ghetti and Giovanni Belardi. The l8th century restoration work on this monument, with its fine marbles and colours, is the subject of a book by Susanna Pasquali. Archaeological excavation and restoration have provided objective data on which to base our observations.
In 1986 Godfrey and Hemsoll  put forward a new theory on the original function of the monument: "an imperial audience chamber". Subsequently, Hemsoll, Davies and Wilson Jones  published a plausible hypothesis on the size of the pronaos in the original design. In his book, Das Pantheon in Rom, Abbild und Mass des Kosmos , published in 1999, Sperling analysed the whole monument in terms of first century AD. mathematics and gnomonics. Although the most important works we have on the architecture and understanding of the Pantheon remain those by De Fine Licht in 1968  and MacDonald in 1976 , respectively, Sperling's book revolutionizes our knowledge of the monument in terms of its relation to neoplatonic mathematics. It is not easy to follow on from Sperling with new arguments and his book requires careful and meditated reading.
Gert Sperling has carried on from where Herman Geertman left off in his celebrated 1980 study "AEDIFICIVM CELEBERRIMVM, studio sulla geometria del Pantheon" . Sperling's conclusions also make use of previous works by Jacobson, 1986 ; Alvegard, 1987 ; Haselberger, 1995 ; Williams, 1997 . It is as if Sperling is taking a "peripatetic stroll" inside the monument in the company of all these writers, with me tagging along behind, a little boy led by the hand, with the work I wrote in 1989 . Sperling's book has several merits which I wish to underline:
I do not wish to list all those who have written on the Pantheon after De Fine Licht. I will mention only Howard Saalman  and William Loerke . In effect a rational bibliography on the Pantheon would be a very useful publication. It would certainly include Rodolfo Lanciani and especially Antonio Michetti and Fabrizio Esposito , respectively professor and disciple in the science of construction, for breaking new ground in their study on the reconstruction of the proportionment of the dome structure by means of classical geometry, 1995-1996; unfortunately literary sources are silent on this subject. We know from Hero of Alexandria about the statics of columns and architraves, but there is nothing from that period on vaults.
Many studies on the Pantheon are carried out far from Rome and so ideas on the monument cannot be checked easily or frequently. For this reason, together with a group of architects and archaeologists working in Rome , I thought it might be a good idea to try and resolve some seemingly banal but still unanswered questions:
In charge of this programme is Riccardo Migliari, professor of the Department of Representations and Reliefs at Rome University "La Sapienza" (Fax 06 49 91 88 84). Working in collaboration with him are Mark Wilson Jones of Bath University, Matthias Bruno of Rome University "La Sapienza", Cinzia Conti of the Rome Archaeological Office and Giovanni Belardi, Director of the Pantheon. There will be a web site for the data so that it may be utilized also by those far from Rome. I hope Prof. Migliari will be able to present these results here, at Nexus IV, next year. Gert Sperling has given his full backing to the project, and has suggested taking weekly readings of the sun at the same time on the Rome meridian. All suggestions are welcome and this is why I have included in the text the fax numbers of the Office and the Department.
A question that is often asked is: Could the inside of the Pantheon have been an astronomical observatory? The Golden House of Nero was another building which was architecturally inspired by the sun and, according to Suetonius, "the main hall, a rotunda, went round according to the motion of the earth, with perpetual motion day and night"; but it was definitely not an astronomical observatory. This aspect has been discussed by Cesare D'Onofrio in a chapter of the new edition of Gli Obelischi di Roma, 1992. However I think the eye of the Pantheon is too small to be an astronomical observatory and too large to be a gnomonic hole; in San Petronio, Bologna, for example, the gnomonic hole of the meridian is only 27 mm wide. Moreover, in the history of gnomonica scientia, the discovery of the use of a ray of light passing through a hole is attributed to Ibn Yunis, a Muslim astronomer active in Cairo and who died in 1009 AD. However D'Onofrio's theory is stimulating and next year we hope to have some precise answers. Mathematical analysis of architecture is scientific by definition. The method is scientific because it is based on numbers and theorems, but the result is not always scientific because we cannot repeat an experiment the way it was done by Galileo Galilei: we cannot always be certain that a mathematical observation we make corresponds to historical fact, that is, the intention of constructing a building according to a mathematical rule that modern research may have discovered. We must be honest with historians working with Latin and Greek, who put their trust in mathematicians, rnethods used in philology and logic being so similar. In order to clarify matters I would like to suggest adopting certain criteria, at least with regard to ancient architecture, which is where my everyday work lies.
After having formulated these criteria I feel like Lucian's Menippus, the cynic-philosopher, who, in the Dialogues of the Dead, desecrates the myths of Olympus and the behaviour of men. For this reason people called him ton kuna ( tòn kùna), the dog that bites with irony.
Lucian, who was in Rome at the time of Hadrian, wrote famous descriptions of works of art; in fact he is considered the founder of art criticism and a particular literary genre, the ekfrasis (ékphrasis), which, in fact, means description. One of these descriptions is entitled The Room and is about architecture and oratory. Lucian's room is not that of any particular building but a model room: it is rectangular, apsidal, facing the east; "the relationship between length and width and between these and height is harmonious". Lucian speaks of "invincible pleasure to the eyes" and says that "words decorate" architecture, and in so doing underlines the risks of art criticism. Moreover, Lucian maintains that architecture and oratory are aimed at "the common man" and "the cultured man". Towards the end of the Classical world, similar criteria of aesthetics can be found in Procopius, who wrote On the Buildings of the Emperor Justinian. In these writers, architecture is a complex organism, which unites matter and ideas in an aesthetic perception that is harmonious, not divided, as it is for us moderns, into humanistic perception and geometrical perception. On the other hand, it is true that in the Classical world mathematics is aesthetics; mathematicians used similes taken from architecture: Nicomacus of Gerasa, a contemporary of Hadrian, uses bridges and ladders to explain how mathematics leads to epistemology.
The exceptional flowering of mathematical studies on the Pantheon is due to its eminent architecture and the shapes of its interior space: it is the greatest example in the world, peri sfairas kai kulindrou (perì sphaìras kài kulìndru), of Archimedes' sphere and cylinder, that is, one inscribed in the other. In antiquity, these shapes helped students learn Archimedes' universal law, 4/3 pr3. Archimedes had these shapes inscribed on his tomb, where Cicero was to see them; but man walks inside the sphere and cylinder of the Pantheon, like in the kosmw (kòsmo): a Greek word with three meanings, "order", "beauty", "world". This is a summary of the work I wrote in 1992, but this is not my aim here. In studies on works of art, gnosiology always surpasses ontology; that is, the problem of the knowledge of something surpasses its reality. We have more studies on the significance of the Pantheon than on its structure: for example, our knowledge of the dome is still based on Piranesi's etchings and observations made by Alberto Terenzio in the thirties.
The boom in mathematical studies on the Pantheon is also due to a quality of mathematics: an important theorem generates numerous corollaries, not always known to the mathematician who advanced that theorem. Most modern critics attribute the design of the Pantheon to one of the world's greatest architects, Appollodorus of Damascus, who was also a famous mechanical engineer: this is thanks to the work of Wolf Dieter Heilmeyer, and the great archaeologists before him.
 Maria Teresa Bartoli, "Scaenographia vitruviana: il disegno delle volte a lacunari tra rappresentazione e costruzione" in Disegnare, Rivisat semestrale del Dipartimento di Rappresentazione e Rilievo, Università degli studi di Roma "La Sapienza", vol. V-VI, no. 9/10 (1994), pp. 51-62.
 Fabrizio Esposito and Antonio Michetti, "Il Pantheon: Teoria e tecnica della commodulatio" in "Disegnare, Rivisat semestrale del Dipartimento di Rappresentazione e Rilievo, Università degli studi di Roma "La Sapienza", 13, pp. 69-80.
 Kjeld De Fine Licht, The Rotunda in Rome, Copenhagen, 1968.
 Herman Geertman, "AEDIFICIVM CELEBERRIMVM, studio sulla geometria del Pantheon", in Bulletin Antieke Beschaving, 55 (1980), pp. 203-229.
 P. Godfrey and D. Hemsoll, "The Pantheon: Temple or Rotunda?" in M. Henig and A. King, eds., Pagan Gods and Shrines of the Roman Empire, 1986, pp. 195-209.
 L. Haselberger, "Ein Leibelriss der Vorhalle des Pantheon. Die Werkrisse von dem Augustusmausoleum", Roemische Mitteilungen des Dt. Arch. Instituts, 101, Mainz, 1995, pp. 279-308.
 D. Hemsoll, P. Davies and M.Wilson Jones, "The Pantheon: Triumph of Rome or Triumph of Compromise", Art History, 10 (1987), 133-153.
 D.M. Jacobson, "Hadrianic Architecture and Geometry", in American Journal of Archaeology, 90 (1986).
 William C. Loerke, "A Rereading of the Interior Elevation of Hadrian's Rotunda" in Journal of the Society of Architectural Historians, 49, pp. 22-43.
 William L. MacDonald, The Pantheon: Design, Meaning and Progeny, London, 1976. To order this book from Amazon.com, click here.
 Giangiacomo Martines, "Argomenti di Geometria Antica a proposito della cupola del Pantheon" in Quaderni dell'Istituto di Storia dell'Architettura, 13, 1989.
 Howard Saalman, "The Pantheon Coffers: Pattern and Number", in Architectura, 18, (1988), pp. 122-123.
 Gert Sperling, Das Pantheon in Rom, Abbild und Mass des Kosmos, Neuried,1999.
 Kim Williams, "Il Panteon e la creazione dell'universo, Lettera Matematica Pristem, 24 (June1997), pp. 4-9.
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