The Pantheon: From Antiquity to the Present Read online

87 Moore 1995; Lancaster 2005.

  88 Lamprecht 1985, p. 176.

  89 De Angelis d’Ossat 1938, p. 227; De Caro and Greco 1981, p. 58.

  90 The latter is a very rare example of filling abutments on the extrados with earth. For this observation, I am indebted to Professor Cairoli Fulvio Giuliani, during restoration work on the “Tempio della Tosse” in Tivoli, carried out in the summer of 2001 by the engineer Fabio Taccini under the direction of the architect Stefano Gizzi.

  91 Giuseppe Cozzo, Ingegneria Romana: maestranze romane; strutture preromane, le costruzioni dell’ anfiteatro flavio, del Pantheon, dell’emissario del Fucino, Rome 1928; see also Lancaster 1998, pp. 147–174; Lancaster 2005.

  92 G. Giovannoni, La tecnica della costruzione presso i Romani, Rome 1925, p. 42.

  93 Rowland Mainstone, “Le origini della concezione strutturale della cupola di Santa Maria del Fiore,” Filippo Brunelleschi. La sua opera e il suo tempo. Atti del Convegno Internazionale per il sesto centenario della nascita, 16–22 Ottobre 1977, Florence 1980, pp. 883–892.

  94 G. Rohlfs, Primitive Kuppelbauten in Europa, Munich 1957; G. Simoncini, Architettura contadina di Puglia, Genoa 1960; E. Allen, Stone Shelters, Cambridge, Mass. 1971; P. Oliver, ed., Encyclopedia of Vernacular Architecture of the World, Cambridge 1997; L. Lago, Pietre e paesaggi dell’Istria centro-meridionale. Le “casite,” Trieste 1994.

  95 J. Fleming, H. Honour, and N. Pevsner, The Penguin Dictionary of Architecture and Landscape Architecture, London 1999, p. 47.

  96 Oliver 1997.

  97 Massimo Pallottino, La Sardegna nuragica, Rome 1950; see also G. Lilliu, La civiltà nuragica, Sassari 1982; Franco Laner, Accabadora. Tecnologia delle costruzioni nuragiche, Milan 1999.

  98 Aristotle, “De Mirabilibus Auscultationibus,” Minor Works, fourth century BC, trans. W. S. Hett, Cambridge 1955, p. 281.

  99 For the “Tomba dei Carri,” see S. Di Pasquale, L’arte del costruire, Venice 1996, pp. 229–237.

  100 The third-story drum-barrel vaults are embedded in the dome for up to 8.4 meters from the springing of the dome, halfway up the second row of coffers. At the end of the barrel vaults, the intrados project 1.8 meters from the springing.

  101 Eugène-Emmanuel Viollet-le-Duc, s.v. “Voute,” Dictionnaire raisonné de l’architecture française du XI° au XVI° siècle, Paris 1875, vol. 9, pp. 471–474.

  102 Adam 1984. Rakob 1988, pp. 280–281, disputes Adam’s proposal for the Temple of Mercury at Baiae; see also Taylor 2003, pp. 190–211, and Lancaster 2005, pp. 44–45.

  103 Licht 1968, p. 141.

  104 De Angelis d’Ossat 1938; Lamprecht 1985, pp. 174–177; Lancaster 2005.

  105 G. Heene, Baustelle Pantheon: Plannung, Konstruktion, Logistik, Düsseldorf 2004, p. 57. In Heene’s view, pp. 28–32, four rings of coffers were built by corbeling whereas, in my opinion, just three were built so. According to Mark 1987, p. 146, the coffering lightens the structure by less than 5% of the total mass of the dome.

  106 C. Lévi-Strauss, La pensée sauvage, Paris 1962, pp. 25–27.

  107 E. Comba, Introduzione a Lévi-Strauss, Bari 2000, pp. 82–85.

  108 Lévi-Strauss 1962, p. 25.

  109 Wilson Jones 2000.

  Five Sources and Parallels for the Design and Construction of the Pantheon

  Gene Waddell

  The Pantheon is considered one of the most characteristic examples of Roman architecture, but at the time it was created, it was unusual in many respects. Its design involved a novel combination of elements from a half-dozen different building types: baths, tombs, basilicas, temples, triumphal arches, and theaters. The unprecedented span required a new approach to concrete construction. Only by virtue of its success did the Pantheon become emblematic of Roman imperial monumental architecture.

  Previous studies have done much to identify likely sources for the Pantheon, but so far they have focused on individual features and placed more emphasis on design than on construction. This study explores both aspects, while special emphasis is placed on clusters of features common to the Pantheon and earlier structures. When a cluster of features occurs in a recently constructed, major monument in Rome or its environs, it can be considered a likely source. Of course, other possible sources may well not have survived, and it is also instructive to examine parallels in buildings that, while they may not have influenced the Pantheon overtly, enhance our understanding of contemporary practice.

  Initially, this chapter reviews the principal buildings that have previously been identified as sources. Detailed consideration is then given to significant clusters of individual elements in these and other buildings that are either earlier or roughly contemporary with the Pantheon. A conclusion summarizes the relative importance of the influences that were combined inventively so as to create a new and influential archetype.

  The Four Main Design Elements

  A portico, transitional block, drum, and dome are the four main design elements making up the Pantheon. Earlier buildings provide numerous examples of each of these features, but no earlier building is known to have combined all four of them. Porticoes were initially used in Roman architecture primarily for temples, of which they were an integral part under a common roof. The Pantheon’s portico was unusual in that it was attached to the front with a separate roof.

  A transitional block facilitated the attachment of a rectangular portico to a cylindrical drum; this slab-like block of masonry may be likened to the walls to which Roman architects had previously attached some temples. The Temple of Mars Ultor, for example, butts up to the firewall that separates the Forum of Augustus from an adjacent neighborhood. The transitional block of the Pantheon also provided space for stairs, as had been done previously in the back of the semicircular exedras of Trajan’s Baths (discussed in Chapter Seven).

  Prior to the construction of the Pantheon, the largest freestanding cylindrical structures were tombs such as the Mausoleum of Augustus (Fig. 5.1a and b). Their walls were windowless, like the Pantheon’s drum. A thick circular drum also provided the most even support for a dome, while the addition of a portico helped to distinguish this project from a tomb.

  5.1. Plan of the Mausoleum of Augustus (a) and plan of the Pantheon (b) at both pavement level and at the springing of the dome, not to same scale. (Wilson Jones 2000, Figs. 4.6, 9.14)

  The largest number of design features adapted for the Pantheon were used previously in Imperial Roman baths (thermae), the building type that had most fully demonstrated the potential of concrete on a large scale. A dome with an oculus had been used in baths for more than a century, but only as part of a larger complex, and not as freestanding structures.1

  Major Buildings of Influence

  Kjeld De Fine Licht and William L. MacDonald considered the possible sources of design for the Pantheon, and both of them identified sources of influence in major imperial buildings of the preceding decades. Agrippa’s Pantheon was nottaken into account as a probable source by these authors because at the time they wrote, it was thought to have a completely different shape (see Fig. 1.3). Today, by contrast, there is no question that the name “Pantheon” was adopted from this predecessor, and that its foundations were reused for the present portico and transitional block. It is further possible that a large circular space anticipated the present rotunda, within which a marble floor has been found beneath the existing one, though it is unclear if it was roofed over, and certainly not with a concrete dome.2 The purpose of Agrippa’s Pantheon and the question of its influence on its successor are explored in Chapter Two.3 The prospect that there was deliberate continuity between the projects is an intriguing one, yet it cannot detain us long here since the focus of this contribution is on specific physical evidence and on the details of articulation and construction.

  Licht pointed out similarities with the actual Pantheon in the materials, scale, and details in the exedras of Trajan’s Baths, and he emphasized the importance of bath buildings generally, including several examples at Baiae. MacDonald p
ointed out numerous similarities with Trajan’s Markets. Both scholars considered the Domus Aurea a turning point in the handling of space and light. Both considered the development of individual design features, but neither considered clusters of related elements or methods of construction in detail.4 They noted important similarities, but differences also need to be taken into account in order to determine which sources were most likely to have had the most direct influence on the Pantheon.

  Trajan’s Baths were constructed just northeast of the Colosseum from AD 104–109 over the top of the Domus Aurea; this immense complex set the standard for the imperial baths that were later constructed by Caracalla and Diocletian. The main space was the grandiose frigidarium with its triple cross-vaults and a span of about 85 Roman feet, while the complex also included several domes and half domes. Two domed halls were approximately 75 Roman feet in diameter (or half that of the Pantheon), but these differ in that they were inserted into square envelopes that were integral to the main building (Fig. 5.2). There also survive three exedras open to the air with half domes that are about 100 Roman feet across or nearly two-thirds as wide as the Pantheon with equivalent coffer patterns (Fig. 5.3).5

  5.2. Plan of Trajan’s Baths. (Diagram Italo Gismondi, in Nash 1962, Fig. 1283)

  5.3. Pair of exedras in Trajan’s Baths; the coffering only aligns with the niches on the main and diagonal axes. (Wilson Jones 2000, Fig. 9.22)

  Trajan’s Forum, dedicated in AD 112, was the culmination of the sequence of imperial fora. Trajan’s was the largest that had been constructed in Rome, and it included a public square, a basilica, two libraries, and Trajan’s Column (Fig. 5.4). The interior of the Basilica Ulpia had a span of 85 Roman feet, similar to that of the frigidarium of Trajan’s Baths, but in this case only the pair of side aisles were vaulted. As in earlier basilicas, the central space had a roof with wooden trusses resting on two stories of columns, and the upper level had a clerestory. The Pantheon’s dome spanned nearly twice this distance with masonry rather than wood, yet there is a dimensional similarity with the large exedras at each end of the nave that were approximately 150 Roman feet in diameter. Like the nave, these exedras were covered with a wooden roof. Depictions on coins indicate that the main entrance had a portico with a quadriga.6

  5.4. Imperial Fora, Rome, including Trajan’s Forum and Trajan’s Markets. (Courtesy of James Packer)

  Trajan’s Markets were built adjacent to the Forum about the same time (Fig. 5.5). The six-storied complex includes at least 170 barrel-vaulted rooms that were probably rented as shops or used as imperial offices, but its precise function is uncertain. The complex was built against the southwest end of the Quirinal, which was cut back to create Trajan’s Forum. The largest space, the Market Hall, has six cross-vaults. With its span of nearly 30 Roman feet and length of roughly 110 feet, and being well lighted by a clerestory, it is one of the most impressive surviving examples of Roman vaulting. The Markets were constructed almost wholly of brick-faced concrete with masonry vaulting throughout.7 Concrete was used in highly innovative ways, and some of the methods that were either introduced here or in other Trajanic buildings found application in the Pantheon.

  5.5. Trajan’s Markets. (Waddell 2008)

  The Domus Aurea, or Golden House, of Nero was designed by Severus and Celer and built from AD 64 to 68. It covered a vast area from the Oppian Hill to the Palatine that was later built over by structures that included, in addition to Trajan’s Baths, the Colosseum, Titus’s Baths, and the Temple of Venus and Rome. Part of the complex that survives beneath the platform constructed for Trajan’s Baths includes an octagonal domed room built of concrete. This room greatly impressed Nero’s contemporaries, and it is widely believed to represent a turning point in Roman architecture. For MacDonald, it “represents the first culminating stage in the creation of centralized interior architecture” (with the Pantheon as the second stage), and he noted that in its interior “shape, space, structure, and light are interlocked as one.”8 In this volume, Giangiacomo Martines has provided additional support for this building as a probable source for the design of the Pantheon. Its main space is the earliest surviving polygonal room that demonstrated the potential of concrete to create an unusual and dramatically lighted space (see Fig. 4.8). Soon afterwards, Domitian’s Palace was constructed with unusual vaulted spaces, but they are also less likely to have influenced the Pantheon than the larger and more recently constructed public buildings of Trajan’s reign.

  Beyond the vicinity of Rome, Baiae has the largest concentration of major domes. Four domes have been called temples, although most if not all of them were parts of baths. They differ from the Pantheon in being constructed as relatively thin shells, and they lack coffering. Only one is unquestionably earlier.9 This, the Temple of Mercury, was probably built a century or more before the Pantheon, and it displays a quite different method of construction. It has a span of 21.55 meters or about 73 Roman feet, and even though it is partly filled with silt and water, it provides a good impression of how domes of equivalent size in Trajan’s Baths must have looked. The largest of the three domes at Baiae is the octagonal Temple of Diana, which, at 29.5 meters in diameter, is nearly two-thirds as wide as the Pantheon, but this dome is relatively pointed in profile. It has generally been dated to the second century AD or to the early third century. The octagonal Temple of Venus, which had a span of 26.3 meters, probably dates later in the second century AD than the Pantheon. Although its walls are substantially intact, little of its dome survives. Unlike the Pantheon, both the Temple of Diana and the Temple of Venus have windows in their walls.10

  Licht and MacDonald noted a number of buildings at Hadrian’s Villa that are more likely to be parallels than influences depending on when they and the Pantheon were constructed (see Chapter Three in this volume). The villa was constructed near Tivoli and almost entirely during the reign of Hadrian, from AD 117 to 138. Over an extensive site, about 2 kilometers long and from 0.5 to 1.0 kilometers wide, dozens of major buildings have survived, singly or mostly arranged in scattered groups. All were constructed of concrete, but unlike the brick-faced concrete of the Pantheon, here it was typically faced with wide bands of opus reticulatum (blocks of tufa arranged in a diagonal net-like pattern) alternating with narrow bands of brick. Many structures at the villa have domes or half domes, and some domes are hemispherical and have an oculus. Other domes and half domes have vertical segments that resemble a pumpkin or gourd, shapes that are noteworthy for the sophistication of their conception and the difficulty of their execution. The “Maritime Theater” is an island villa or retreat within a cylindrical drum that has nearly the same diameter as the Pantheon’s interior (Fig. 5.6).11

  5.6. So-called Maritime Theater, Hadrian’s Villa, Tivoli. (Photo author in 1982)

  MacDonald mentioned the probable influence of cylindrical tombs, including that of Caecilia Metella. He also discussed the possible influence of the Greek tholos, the other main type of freestanding circular building that had been previously constructed in Rome. Examples include the Round Temple by the Tiber, the so-called Temple of Sibyl at Tivoli, and the tholos in the Largo Argentina. All three of these examples had a peristyle around a small cella with an internal diameter of about 25 Roman feet.12 Vitruvius (4.8.3) refers to domes on circular peripteral temples, but these examples are more likely to have had a wooden roof like all known Greek examples. At most, therefore, they are only indirect sources for the Pantheon.

  Parallels for Design and Sources for Structural Elements

  The most significant design elements present in the Pantheon are as follows: (A) a freestanding building with an attached and pedimented portico, (B) a transitional block with stairs, (C) a cylindrical drum without windows, (D) a dome with coffers and an oculus. There are also a number of (E) other design features that had been used in Roman architecture: cross axes for a circular plan, immense monolithic shafts of granite, an internal clerestory, the use of bilateral symmetry, an orthogonal floor pattern fo
r a circular plan, and a different elevational treatment of the attic compared with the main interior order. All parts of the design were interrelated using (F) simple proportions characteristic of Roman architecture. The most significant structural elements are (G) a dome with its base constructed of rings of concrete (step-rings) separated by layers of brick, (H) a cellular wall on multiple levels, (I) concrete with horizontal layers of aggregate, (J) “relieving arches” of brick-faced concrete, and (K) concrete vaults with brick laid flat against their intrados.

  (A) Freestanding Building with an Attached and Pedimented Portico.

  As already noted, a portico was usually an integral part of the overall form of temples, under the same gabled roof. Attached porticoes were less common, and they might or might not have had a pediment. Round temples ordinarily had encircling peristyles rather than projecting porticoes. In having an attached portico with a pediment, the Pantheon resembles some earlier transverse temples such as the Temple of Concord, which had a rectangular cella with a portico on one of its longer sides. During the Roman Republic, pedimented porticoes were ordinarily reserved for sacred structures, but their use became more widespread over time.13 Basilicas generally had porticoes without pediments.14 As mentioned, the Basilica Ulpia (Fig. 5.4) had an unpedimented portico in the center of a longer side, and the Basilica Nova was redesigned to have an unpedimented portico on a long side as well as at one end.15