The Pantheon: From Antiquity to the Present Read online

  11 MacDonald and Pinto 1995, pp. 28–29 (site description). For detailed accounts of excavations, see S. Aurigemma, Villa Adriana, Rome 1961. For dates of construction, see A. C. G Smith, “The Date of the Grandi Terme of Hadrian’s Villa at Tivoli,” Papers of the British School at Rome 46, 1978, pp. 73–93.

  12 Dimensions for these buildings are given by Wilson Jones (2000, pp. 217–219). Although Renaissance architects such as Palladio reconstructed such tholoi with domes, I have been unable to find any dome fragments for these three examples. The entablatures of the two tholoi in Rome have been destroyed, and at Tivoli nothing of the wall survives above the level of the entablature (Richard Delbrueck, Hellenistiche Bauten in Latium, Strassburg 1907, Figs. 18 and 28). Unlike the Pantheon, the tholos in the Largo Argentina has a podium and an altar in front of its steps and so was unquestionably a temple. Although it has been considered a possible source for the Pantheon, the date when its portico was added is uncertain, and it did not have a transitional block. MacDonald (1976, pp. 67–68; Figs. 77–78) judged this tholos to be a “remote precedent,” but he observed that adding a portico to a drum “had not been done before” [the Pantheon]. For Licht, this tholos was not “either a basis or even a model,” but was worthy of note (Licht 1968, pp. 218–219). He knew of no definite evidence for an earlier rotunda that was freestanding (p. 207). The Hellenistic Arsinoeon at Samothrace was large (about 60 feet in diameter), cylindrical, and freestanding, but it was roofed with wood, and it was not nearby, not contemporary, and not well known (cf. MacDonald 1976, p. 49 and Figs. 42 and 51).

  13 Godfrey and Hemsoll 1986, p. 204.

  14 For persuasive evidence that the Pantheon was intended to have a taller portico with a gabled roof, see Paul Davies, David Hemsoll, and Mark Wilson Jones, “The Pantheon: Triumph of Rome or Triumph of Compromise?” Art History 10, 1987, pp.133–153, and Wilson Jones 2000. Chapter Seven here provides further evidence (including foundations that could support larger columns and the set-back in the profile of the transitional block that ties in with the upper pediment).

  15 Blake 1973, pp. 12–15, n. 65; p. 17. Spartianus, Hadrian 19.9–10. Rodolfo Lanciani, Forma Urbis Romae, Rome 1893–1901, repr. Rome 1988.

  16 Jürgen J. Rasch, Das Mausoleum bei Tor de’ Schiavi in Rom, Mainz 1993. C. Briggs, “The ‘Pantheon’ of Ostia (and Its Immediate Surroundings),” Memoirs of the American Academy in Rome 8, 1930, pp. 161–169; frontispiece and Plates 51–57. R. Meiggs, Roman Ostia, 2nd ed., Oxford 1973. On the possible exception, the tholos in the Largo Argentina, see n. 12 herein. Wilson Jones 2000 (p. 182 and Fig. 9.6) notes similar plans of earlier circular buildings at Stymphalos and Athens, but neither is known to have been domed.

  17 Lynne Lancaster, “Concrete Vaulted Construction: Developments in Rome from Nero to Trajan,” Ph. D. diss., Oxford 1996, pp. 103–104, 247. The plan of Trajan’s Baths by Gismondi (Fig. 5.2 herein) designates the three best-preserved exedras differently from the plan in Licht’s 1974 monograph; Gismondi’s B, F, and C are Licht’s H, L, and D, respectively.

  18 Square coffers had been used centuries earlier to articulate flat ceilings in Greek temples, and were adapted and used nonstructurally by the Romans for concrete structures. Roughly, square coffers had been used as early as about 100 BC on a double-curving barrel vault at Praeneste (Palestrina). In the Pantheon, coffers are a major unifying element of the interior. As MacDonald (1976, pp. 72–74) pointed out, their corners align in such a way as to create the impression of interlocking spirals. The effect achieved is similar to that of the diamond-shaped coffers in the apses of the Temple of Venus and Rome as rebuilt around AD 300.

  19 Charles Cameron, The Baths of the Romans Explained and Illustrated: with the Restorations of Palladio Corrected and Improved, London 1772, Plate 7. Yegül (1992, p. 146) gives the somewhat larger dimension of 27 meters.

  20 Licht 1974, Supplementum, Fig. 8 “S.”

  21 The Tor de’ Schiavi and the Rotunda at Ostia have similar arrangements.

  22 Wilson Jones (2000, pp. 194–196) lists other means used to emphasize axes inside the Pantheon, some of which are so subtle as to be easily overlooked.

  23 M. E. Blake, Roman Construction in Italy from Tiberius through the Flavians, Washington, DC 1959, pp. 89–90. Rose granite was used for the Temple of Peace and gray for the Basilica Ulpia.

  24 Packer 1997, p. 434; Wilson Jones 2000, p. 223.

  25 Some city gates had similar arrangements with openings aligning rather than orders of different sizes (cf. Wilson Jones 2000, p. 116 and Fig. 6.12). On the exterior of the Pantheon, the largest cornice is at the top of the wall (as for the Colosseum), but on the interior, the largest cornice was used with the larger order, and the smaller order was treated more like the attic story of a triumphal arch (cf. Licht 1968, Figs. 99 and 100).

  26 William C. Loerke (“A Rereading of the Interior Elevation of Hadrian’s Rotunda,” Journal of the Society of Architectural Historians 49, 1990, pp. 22–43) discussed convincingly how the attic story of the Pantheon’s interior reflects the structure of the building.

  27 Licht 1974, Plates 1 and 3. On size and proportion in Roman architecture, see Wilson Jones 2000.

  28 The width between the centers of end columns on the front of the portico is 32.03 meters and the height of the transitional block is 32.23 meters (Wilson Jones 2000, p. 220).

  29 Packer 1997, folio 24. MacDonald and Pinto 1995, p. 82. In his book on the Pantheon, MacDonald makes a detailed comparison of the Forum of Augustus and the Pantheon, particularly in regard to the possible meanings that both buildings had for the Romans (MacDonald 1976, pp. 84–91). Most notably, the exedras of the Forum have a radius of 75 feet, the same radius as the Pantheon, but were not vaulted and were not fully hemispherical. Their influence would have been primarily in terms of scale.

  30 On the use of whole number or “round” dimensions, see Mark Wilson Jones, “Principles of Design in Roman Architecture: The Setting out of Centralised Buildings,” Papers of the British School at Rome 57, 1989, pp. 106–151; Wilson Jones 2000, pp. 71–84.

  31 The Pantheon’s diameter from wall facing to wall facing is 43.57 meters (147.20 Roman feet) and from column center to column center is 44.52 meters (150.41 Roman feet); Wilson Jones 2000, p. 220.

  32 The order of the attic including its running pedestal is 30 feet tall, and the order of the main story is 45 feet (Wilson Jones 2000, p. 185).

  33 Wilson Jones 2000, pp. 135–156.

  34 A ratio of about 1:8 was considered sufficient for most domes and about 1:10 for most barrel vaults (Wilson Jones 2000, pp. 82 and 233 n. 38, citing Janet DeLaine, The Baths of Caracalla in Rome: A Study in the Design, Construction, and Economics of Large-Scale Building Projects in Imperial Rome (Journal of Roman Archaeology, Supplement 25), Portsmouth, R.I., 1997; Jürgen Rasch, “Zur Konstruktion spätantiker Kuppeln vom 3 bis 6 Jahrhundert,” Jahrbuch des deutsches Archäologischen Instituts 106, 1991, pp. 311–383).

  35 Through-courses had earlier been used intermittently in the Colosseum and in Trajan’s Baths (Lancaster 1998, p. 285). In the Mausoleum of Augustus, horizontal sections of concrete were separated by layers of limestone chips (personal observation; cf. H. Von Hesberg and S. Panciera, Das Mausoleum des Augustus. Der Bau und seine Inschriften, Munich 1994). In Domitian’s Nymphaeum at Albanum, the sections were separated by layers of pozzolana (Blake 1959, p. 138).

  36 Lancaster 1996, vol. 1, p. 209, and Fig. 110B.

  37 D. Moore, The Roman Pantheon: The Triumph of Concrete, Wyoming 1995. Francesco Piranesi, Seconda parte de’templij antichi che contiene il celebre Pantheon, Rome 1790, Plates 10 and 29, illustrated two different structures for the dome of the Pantheon. In the earlier version, he showed brick ribs, but in the later one, he showed that the step-rings were separated by through-courses. Horizontal layers of bricks (tegole) had been shown previously on the intrados by Antonio da Sangallo il Giovane (Waddell 2008, Fig. 58B).

  38 The span of the Serapeum is about 54 feet or
approximately one-third as much as the Pantheon (R. Vighi, Villa Hadriana, trans. J. B. Ward Perkins, Rome 1958). Another similarity shared with the Pantheon is that of nonalignment; the seven segments of the vault of the Serapaeum do not align with the nine openings in its walls (MacDonald and Pinto 1995, p. 112).

  39 Being so much smaller, the Serapeum could conceivably have been completed early enough to have been a source for the Pantheon’s dome. For the excavation of the Serapaeum and the surrounding area of the Canopus, see S. Aurigemma, “Lavori nel Canopo di Villa Adriana,” Bollettino d’Arte 39, 1954, pp. 237–341. Most of the principal buildings at Hadrian’s Villa, including the Serapaeum and Roccabruna, have bricks stamped with the names of consuls for the year 123, and many have stamps from 124 (Herbert Bloch, I bolli laterizi e la storia edilizia romana. Contributi all’archeologia e alla storia romana (1936–1938), Rome 1947, pp. 137–141). The Piazza d’Oro and the domes of the Large and Small Baths have brick manufactured a few years later. A total of 279 brickstamps with the names of consuls were found while excavating the Canopus from 1950 to 1955, and they were analyzed by Domenico Faccenna: 189 were manufactured in AD 123, 11 in AD 124, 17 in AD 125, 61 in AD 126, and 1 in AD 127 (Aurigemma 1961, p. 127).

  40 Piranesi was probably also misled by the use of these ladder-like ribs during the Severan period for renovating a part of Agrippa’s Baths known as the Arco della Ciambella, particularly since it lies so close to the Pantheon and was also believed to have been created by Agrippa. See Licht 1968, p. 297.

  41 MacDonald and Pinto 1995, p. 113. Martines also emphasizes the importance of these wall cells for the construction of the Serapeum and the Pantheon (Giangiacomo Martines, “La struttura del Pantheon velut regionem fornicatam,” Quaderni dell’Istituto di Storia dell’Architettura 41, 2004, pp. 3–16, p. 7 n. 29, and Chapter Four in this volume).

  42 Von Hesberg and Panciera 1994, Figs. 1 and 2 and Plate 3c.

  43 Lynne Lancaster, Concrete Vaulted Construction in Imperial Rome: Innovation in Context, Cambridge 2005, p. 167.

  44 Alberto Terenzio, “La Restauration du Panthéon de Rome,” Museion 20, 1932, Plates 10–11.

  45 J. DeLaine, “Structural Experimentation: The Lintel Arch, Corbel, and Tie in Western Roman Architecture,” World Archaeology 21, 1990, pp. 416–417.

  46 Lancaster noted that the earliest “relieving arches ... of bricks or tiles” were used in the Augustan period and that bricks were used later to create “voussoirs” of concrete (Lancaster 2005, pp. 88 and 94). However, she usually interpreted vaults faced with bipedales as having a solid arch of bipedales rather than as being made of concrete voussoirs. She reconstructed the great arches of the Pantheon as consisting wholly of bipedales (2005, p. 97; Fig. 80).

  47 The broad arch that serves as the main entrance to the main hall of Trajan’s Markets shows on the intrados that most of its bipedales extend much less than two feet into the concrete. A prerestoration set of photographs made of Trajan’s Markets shows that the arches of its hemicycle were also constructed using concrete voussoirs (Instituto Centrale per il Catalogo e la Documentazione, Ministero Beni e le Attivita Culturali). One photograph from this series is reproduced by Giovanni Teresio Rivoira (Roman Architecture and Its Principles of Construction Under the Empire with an Appendix on the Evolution of the Dome Up to the 17th Century, New York 1972, a translation of Rivoira, Architettura Romana, Milan 1925), Fig. 126. Arches with flat lintels were made of concrete as early as the end of the second century BC (DeLaine 1990, pp. 416–417).

  48 This aqueduct was constructed of concrete by Nero and was reinforced using concrete in ca. AD 201 by Septimius Severus and Caracalla (Esther Boise Van Deman, The Building of Roman Aqueducts, Washington 1934, pp. 266–270).

  49 The consensus of opinion is that the Pantheon’s great arches are made wholly of bipedales and mortar rather than concrete with a brick facing: Auguste Choisy, L’art de bâtir chez les Romains, Paris 1873; Rivoira 1925; Terenzio 1932; Licht 1968; MacDonald 1982; Moore 1995; Lancaster 2005; Gerd Heene, Baustelle Pantheon: Planung, Konstruktion, Logistik, Düsseldorf 2004; Giovanni Belardi, Il Pantheon: storia, tecnica, e restauro, Viterbo 2006.

  50 The function of a buttress is primarily to resist lateral thrust, while the function of an arch is to support and transfer weight to either side of an opening. For a diagram with the buttresses of the main hall in Trajan’s Markets see MacDonald 1982, Plate 93. How the buttress on the south side of the Pantheon terminated is uncertain. Licht (1968, p. 159) reconstructs a half arch extending upward against a wall of the Basilica of Neptune. Heene (2004, p. 63) reconstructs a half arch extending downward above the apse of the basilica.

  51 J. H. Middleton, The Remains of Ancient Rome, 2 vols., London 1892, pp. 1, 60.

  52 For the extensive use of brick linings for the concrete vaults in Trajan’s Markets, see Lancaster 1998, p. 283; Lancaster 2000; Lancaster 2005, pp. 31, 32, 176, and 207.

  Six The Pantheon Builders: Estimating Manpower for Construction

  Janet DeLaine

  Introduction

  The Pantheon has long had iconic status, universally acknowledged as the greatest achievement of Roman architecture and one of the wonders of the Roman world. The unparalleled clear span of the dome particularly impressed later architects and engineers, who used it as a point of reference for their own wide-span structures, including the domes of Santa Maria del Fiore in Florence, St. Peter’s in Rome and St. Paul’s in London, and even the great Victorian train sheds of St. Pancras Station.1 A major part of the universal fascination with the building lies in its complex structural system and the constructional processes employed, particularly in relation to the dome.2 Because of the difficulties we have with understanding the Pantheon as a structure, it has been natural to imagine that it was also an exceptionally difficult, time-consuming, and labor-intensive construction project for the Romans. The aim of this chapter is to test some of these assumptions, using a method of reverse quantity surveying, originally developed for the Baths of Caracalla in Rome.3 This can provide a rough estimate of the minimum manpower requirements for the actual construction on site (excluding all labor relating to the production, supply, and transportation of materials to the site), as well as the minimum construction period. Although the calculations can yield only approximate and hypothetical minimum figures, they at least provide an idea of the scale of the project in terms of manpower, and allow us to test whether this really was the “mammoth undertaking” assumed by many scholars.4 This also has implications for how we see the Pantheon as part of the building projects of Trajan and Hadrian.

  Construction Analysis

  The first requirement in estimating manpower is an understanding of the physical fabric in order to calculate volumes of materials and assign human actions to putting them into place. In essence, the Pantheon, as can be seen in the set of line drawings published by Kjeld De Fine Licht (Figs. 6.1–6.5), consists of a circular drum (the rotunda), divided in plan into eight piers by alternately rectangular and semicircular recesses. This drum supports a dome that is roughly hemispherical in profile on the inside, while the exterior of the drum is divided into three zones (lower, middle, and upper), the upper zone rising to approximately one-third of the height of the dome. On the entrance side there is a rectangular structure (the intermediate block), which links the rotunda to the columnar pedimented portico forming the main facade. The intermediate block is also divided by cornices into three registers, equivalent to the three exterior zones of the drum. At the opposite end, at the rear of the rotunda, is a series of parallel barrel-vaulted chambers (the grottoni) built between the Pantheon and the probably contemporaneous Basilica of Neptune to the south (Fig. 6.5).5 The Pantheon once sat at the head of acolonnaded precinct, but this will not be included in the calculations here. While it is not necessary for the purpose of this exercise to describe the whole of the fabric of the building in detail, some explanation will be givenfor the assumptions and approximations used where evidence is limit
ed or details are open to various interpretations.

  6.1. Ground plan. (Licht 1968, Fig. 98)

  6.2. Half plans of upper levels. (Licht 1968, Fig. 97)

  6.3. Half sections through the rotunda. The annotations refer to different types of aggregate, for which see Fig. 1.12. (Licht 1968, Fig. 99)

  6.4. Longitudinal section. (Licht 1968, Fig. 105)

  6.5. Isometric rendering from rear, showing the so-called grottoni (grottoes), the Basilica of Neptune, and the triple-arched connection or “bridge” between the two at high level. (Licht 1968, Fig. 175)

  The Rotunda, Intermediate Block, and Grottoni

  The rotunda and intermediate block, while not entirely without difficulty, are the easiest parts of the Pantheon to analyse in terms of construction and have been the parts most discussed in the literature.6 Much less has been written about the grottoni, but the basic construction of the lower parts is virtually identical to that of the Rotunda. All walls are made of a uniform brick-faced concrete, with approximately 70 pieces of brick per square meter of facing, based on the average size of the brick pieces and the mortar joints. The materials of the core are less easy to measure and, as is well known, the caementa (rubble aggregate) in the rotunda change through its height. Nevertheless, the size of the pieces of rubble does not necessarily change, remaining roughly fist sized, and what evidence we have suggests that an average figure of 5,000 pieces of caementa per meter cubed is a sensible assumption.