Excerpted from Chapter 4 - The Campus Martius
The Pantheon Unexplained
Rivers of ink and forests of paper have been devoted to the Pantheon, the strangest of all
buildings that have come to us from antiquity. The large, light and stable dome with its oculus does not
match up with the porch. The inscription proclaims that Agrippa built it but bricks date it to over a century
after his death.
Columns are of different heights, stairs buried,
halls walled up, two pavements lie below it and two pediments before it.
Was the rotunda with its oculus built by Agrippa, then restored by the emperor Hadrian?
Or was the whole thing built by Hadrian? Or by Trajan? Could the famous
hemispherical interior with its rectangular front be just an accident due to restoring and
re-using a damaged building?
First proceed diagonally across the Piazza della Rotonda, past the fountain, to the corner of the piazza and Via dei Pastini, where there is a little bar (2014). This is just about the only spot from which the rectangular “transitional block” and the double pediment of the Pantheon can be seen.
Below: The higher pediment on the transitional block of the Pantheon, from Via dei Pastini.
What was the reason for the higher pediment? The usual explanation is “they ran out of 50-foot (Roman feet) granite shafts”, and having only 40-foot shafts, had to build the portico much lower. Yet there is no proof for this and not all archaeologists accept that idea.
An interesting thing about the lower pediment was the find made in the 1930s on the
travertine pavement in front of the Mausoleum of Augustus. Lines drawn in that pavement show that the stones for the
pediment were cut and set up there, flat on the ground, before being transported here and
mounted. The ground height of the stonecutter’s incised lines, much higher than
the ground level of the tomb, tells us that
this work was done when both Agrippa and Augustus were long dead, perhaps as much as a century later:
the time of emperor Hadrian.
Finally, the inscription on the pediment:
M · AGRIPPA · L · F · COS · TERTIUM · FECIT
proclaims that Marcus Agrippa, son of Lucius, built this when he was consul for the third time, which would have been 27 BC. Up to 1890, before brickstamps from ~100-130 AD were found in the rotunda, everyone believed that the Pantheon as it stood was the work of Marcus Agrippa, on the basis of this sole inscription. But in the biography of the emperor Hadrian (reign 117-138 AD) written in the 4th century AD, the Historia Augustae, we read:
“At Rome he restored the Pantheon, the Voting-enclosure, the Basilica of Neptune, very many temples, the Forum of Augustus, the Baths of Agrippa, and dedicated all of them in the names of their original builders.”
Quod non fecerunt barbari...
“What the barbarians did not do, the Barberini did.”
Next proceed into the grandiose eight-column portico leading to the entrance, and have a look at its humble ceiling.
Below: The wooden ceiling of the portico.
Here we are looking at bare roof tiles resting on wooden beams, instead of the bronze beams and bronze suspended ceiling that survived until pope Urban VIII Barberini (pontificate 1623-1644) removed them in order to cast 110 cannons for Castel Sant’Angelo.
And below this humble ceiling is the only door in the rotunda,
the great double bronze door which was long thought to be a later
replacement for the original, mainly because of the frame on either side
and the grille above, which caused archaeologists to comment that it was too small for
In fact, when at last the bronze was carefully studied, these were found to be
original Roman doors, one of the rare survivals of monumental bronze.
They had been cleaned in the course of the centuries, Christian motifs applied, but analysis
of the fusion technique left no doubt that they date from the empire.
Below: The doors of the Pantheon, as they were in 1976, with the right door stuck shut. Photograph © Paula Chabot, from the VRoma Project.
The Eye to the Heavens
It is only once you are inside that the power of the Pantheon becomes clear: it is the
huge dome and the
oculus in its centre, even on days when rain is pouring through it.
Below: The oculus.
The dome was the largest in the world until its diametre of 43.3 metres (142 feet, 150 Roman feet) was surpassed by two metres when Filippo Brunelleschi completed the dome of Santa Maria del Fiore in Florence, in 1436. If we consider that the present dome was built around 100 AD, then it held the record for some 1900 years. It is one of the most studied, and even today we do not fully understand how it was built nor how it has remained intact so long, through earthquakes, settling, fires, and lightning strikes.
Hadrian Slept Here
Hadrian set up a magistrate’s bench where today the main altar is found,
and here presided over cases, petitions, and the meetings of the Senate,
perhaps dozing (and dreaming of exciting travels through the empire, far from
the boring business of the capital).
Below: The main altar of the Pantheon.
Rodolfo Lanciani wrote that in 1828, when the old altar was being removed, columns engraved with the name Vibia Sabina, empress of Hadrian, were found here, although what became of them we do not know.
Which brings us to the use of the Pantheon first as a Christian church, then as a burial site for Rome’s greatest artists, and finally for modern Italy’s two kings. Of all the graves here, the tomb of Raphael is both the humblest and the proudest. His epitaph reads:
Ille hic est Raphael timuit quo sospite vinci
The Baths of Nero
At this point, if you like, a short detour will take you to see
two reminders that the emperor Nero, as well, built baths in this area, about 80 years
“Who was ever worse than Nero? Yet what can be better than Nero’s warm baths?”
The baths are known as the
because they were rebuilt in grandiose style in 227-229 AD by the emperor Severus Alexander. The huge
amounts of stone recovered from their ruins date from that time.
After a few metres up the Salita dei Crescenzi, you can turn left and proceed down the Via di Sant’Eustachio. Two pink granite columns along with a bit of the frieze found in front of the church of San Luigi dei Francesi in 1934 have been set up along the eastern wall of the church of Sant’Eustachio, in an area that was actually behind the baths (the entrance, at least in the third century, was on the north side). You notice we have gone downhill: we have left the ruins of the baths proper.
Below: Columns of Nero’s Baths found at the church of San Luigi dei Francesi.
Turn right at the church of Sant’Eustachio and walk across the Piazza di Sant’Eustachio, to reach the Via degli Staderari (there is usually a policeman on guard, since Palazzo Madama to the right houses the Italian Senate). A labrum, or bathtub, in pink Egyptian granite, converted to a fountain, adorns the Largo della Constituente. The labrum was found under Palazzo Madama and was set up as a fountain here in 1987.
Below: A bathtub, serving as a fountain.
Turn right up the Via della Dogana Vecchia and note how the street slopes upward again as
we enter the central area of the baths.
Isis and Serapis in the Campus Martius
Now that we have been thoroughly confused by the Pantheon, we can turn to a monument that is simpler to decipher, if harder to find, a temple that was vowed to destruction: the great Iseum, Isis Campensis, the temple of Isis in the Campus Martius.
(end of excerpt)
Caldarium or Calidarium: This was the heated room in the baths, also known as a vaporarium or sudatorium. It was also sometimes called a laconicum or laconium from the word “Laconia”, or “Lacedaemonia”, the region inhabited by the Spartans, who were said to have originated the sweat bath. ← Back
The Canonical Form of the Hot Room: In De Architectura, book V, chapter 10, 5, Vitruvius prescribes a hemispherical form for the hot room, its height being equal to its width,
and topped by a dome such that heat and vapour are evenly distributed along the walls. At the apex of
the dome an opening is covered by a round bronze shield suspended on chains. This bronze cover can then
be raised or lowered to regulate the temperature within.
The Fire of 80 AD or the Fire of Titus: Emperor Titus was in Campania inspecting the damage done by the eruption of Vesuvius in 79 AD when a great fire broke out in Rome. According to Cassius Dio, it destroyed huge parts of the Campus Martius and the Capitol:
“the temple of Serapis, the temple of Isis, the Saepta, the temple of Neptune, the Baths of Agrippa, the Pantheon, the Diribitorium, the theatre of Balbus, the stage building of Pompey’s theatre, the Octavian buildings together with their books, and the temple of Jupiter Capitolinus with their surrounding temples. Hence the disaster seemed to be not of human but of divine origin; for anyone can estimate, from the list of buildings that I have given, how many others must have been destroyed.”
The Debate on the Pantheon: To this very day archaeologists are not completely certain about the Pantheon. Some
believe its form to be essentially unchanged since Agrippa’s time (25 BC),
and that it may have developed from the caldarium,
simply because it is built in the
(a hemispherical domed structure with an opening at its summit) and that it is so close to the rest of the
Moreover, the architect who built the Pantheon for Agrippa, Lucius Cocceius Auctus,
was a native of Cumae, near Baia, where a similar
concrete dome with an oculus
topped a caldarium.
Below: Remains of the coffered half-dome of Trajan’s Baths in the Park of Colle Oppio.
Thus, some theorists maintain that the dome of the Pantheon as well was the work of Apollodorus.
Early concrete dome: The “Temple of Mercury” at Baiae is a concrete dome with an oculus at centre, over a caldarium that used natural hot springs. The dome is 21.5 metres (71 ft.) in diameter, about half the size of the dome of the Pantheon. It was built in the 1st century BC, predating the Pantheon. ← Back
Santa Maria ad Martyres: In 609 AD the Byzantine emperor Phocas (reign 602-610 AD), nominally the sovereign of Rome where Pope Boniface IV (pontificate 608-615) was de facto ruler, ceded the Pantheon to the pope for use as a church.
The Importance of the Pantheon: The Pantheon is the best preserved of all classical buildings and one of the oldest, if we believe that at least
some of its surviving parts were built by Agrippa around 25 BC. It became the model for many many other buildings both in the ancient and the modern world: one need only to think of the 18th-century Parisian Pantheon, the British Museum Reading Room, the American Congress building, the Sankt-Hedwigs-Kathedrale in Berlin: the list of libraries, churches, and civic buildings emulating the design of the Pantheon is endless.
IMP CAES L SEPTIMIUS SEVERUS ET IMP M AURELIUS ANTONINUS PANTHEUM VETUSTATE CORRUPTUM CUM OMNI CULTU RESTITUERUNT
The restoration of the Severans must have been very limited, since no stonework or bricks from their time (193-217 AD) have been found. ← Back
The Construction of the Pantheon: Its incredible
stability starts unsurprisingly with the extremely thick wall of the cylindrical drum which supports the dome.
The drum wall is 6.4 metres (21 feet, 40 Roman feet) thick, but is not solid masonry: there are 16 voids in the wall, comprised of eight load-bearing arched barrel vaults and eight blind niches at the lowest level, with smaller cavities above. The foundations are even wider than the wall: a 10-meter wide double ring made of layers of lime and
concrete, extremely hard and waterproof.
Pozzolan or pozzolana: A volcanic pumice or ash which takes its name from Pozzuoli (near Naples) where it is especially abundant.
The Name of the Pantheon: It seems the word “Pantheon”, from the Greek “of all the gods”, was a nickname for this building, since
ancient writers such as Cassius Dio and Macrobius both refer to it as “the so-called Pantheon” and
“the temple they call the Pantheon”. In Hellenistic culture, temples to all the gods or to the
twelve great gods were called Pantheon and Dodekatheon.
Since Agrippa’s temple was dedicated it seems more to the
deified Julians than to all the gods, Romans may have felt that it did not quite deserve the name
Raphael: Raffaello Sanzio of Urbino, one of the great masters of the Renaissance, died at the age of 37 in 1520.
“At noon of September 14, 1833, the last stone was removed, and the excited assembly beheld for the first time the remains of the “divine painter”. [...] At 2.25 P.M., Gaspare Servi announced the discovery of the skull, the leading feature of which was a double set of strong, healthy, shining teeth.”
The remains of Raphael were then placed in a coffin in public view below the Madonna del Sasso. ← Back
Neronian-Alexandrian Baths: The baths
are remembered in ancient sources for their luxury. Like the Baths of Caracalla, they had a network of
underground service tunnels. They were very popular and thus crowded; Severus
Alexander extended their opening hours into the night. They remained in use into the 5th century.
Below: The Baths of Nero mapped onto modern streets.
Since the water from the Aqua Virgo aqueduct was insufficient for these new baths, Severus Alexander built a new aqueduct to supply them, the Aqua Alexandrina, of which there are many remains still standing.
Below: Arches of the Aqua Alexandrina at the Fosso di Centocelle, in the eastern part of Rome.
From the 15th century to the present, mosaics, granite basins and columns, and bits of the frieze have been extracted from the ruins. Two columns in pink Egyptian granite from Nero’s baths were mounted at the northeast corner of the Pantheon when the portico was restored in the 17th century. ← Back
Temple of Isis in the Campus Martius: When exactly it was first constructed is unknown, but Julius Caesar, who as we know had a soft spot in his heart
for the Egyptian queen
may have had a hand in it, directly or indirectly. In any case, the triumvirate of 43 BC (Octavian, Mark Antony, and Lepidus)
voted a temple to Isis and Serapis, probably the temple in the Campus Martius, and possibly as a gesture
meant to enlist Cleopatra on their side in the pursuit of Caesar’s assassins. But this is just a guess.
The Cult of Isis at Rome: There were two major temples to Isis and Serapis by the end of the Republic. The main temple was on the Campus Martius, and known as Isis Campensis, and a smaller temple stood at the foot of the Oppian (on what is now the Via Labicana). The third Augustan Region of Rome took its name from the Oppian temple: Regio III was “Isis et Serapis”.
Cleopatra VII of Egypt: Cleopatra hardly needs any introduction: she is perhaps the most famous woman of the ancient world, even in her own time.
[she] embarked in a little skiff and landed at the palace when it was already getting dark. To escape notice, she stretched herself inside a bedroll, and Apollodorus tied the bedroll up with cord and carried it inside [...]
We can imagine Caesar’s surprise upon unrolling the bedding. He was 51 at the time.
In the “Life of Antony” we read:
When she spoke, it was a pleasure merely to hear the sound of her voice, with which, like an instrument of many strings, she could play in any language she wished. There were few barbarians (non-Greek speakers) for whom she used an interpreter; she spoke without help to the Ethiopians, Troglodytes (people of the coast), Hebrews, Arabs, Syrians, Medes, and Parthians. They say she knew several other languages as well [...]
And her pranks on Mark Antony are also legendary. Apart from serving him her pearl at dinner, she bested him at fishing:
One day when fishing and catching nothing, Mark Antony secretly ordered his servants to dive and put previously-caught fish on his hook. But the queen was not fooled: she called for a new fishing party on the morrow, summoning friends to witness Antony’s prowess. When he cast his line, she had her divers fix a salted Pontus herring to his hook [...]
When captured by Octavian in 30 BC, after the final defeat of Mark Antony, she famously committed suicide by allowing herself to be bitten by an asp rather than be paraded in his triumph. ← Back
Destruction of the Iseum: The emperor Theodosius I (reign 379-395 AD), a Christian, forbade all pagan cults (and also some Christian cults as well, such as Arianism).
The cult of Isis and Serapis
was particularly targeted after the violent reaction of followers of Isis and Serapis in Alexandria in 391,
when Christians were killed and the Serapeum of Alexandria, one of the wonders of the world, was destroyed.
Thus, some archaeologists believe the fire that consumed the
Iseum of the Campus Martius could have equally been a deliberate demolition in response to the events
at Alexandria, mainly because it seems the temple priests were forewarned: they hid many of the
temple’s treasures in a small room. These were found, unharmed, during excavations in the Via del Beato Angelico in 1833.
The Statue of Venus in the Pantheon:
We have this account of the marvellous statue of Venus in the Pantheon from
Pliny the Elder, writing around 77 AD.
The story is actually about the bet that Cleopatra
made with Mark Antony, who “stuffed himself daily with rare foods”.
She could serve a meal so extraordinary, she wagered, that it would be worth 10 million sesterces.
Mark Antony took her on. The next day she
set before Mark Antony a perfectly ordinary meal, at which he laughed, declaring himself winner of the bet.
Cleopatra told him to wait for dessert, which was a glass of vinegar for each. She was wearing at
the time pearl ear-rings, the “two largest pearls of all history, bequeathed to her by kings”.
She took off one pearl, dropped it into the vinegar where it dissolved, and drank it. As she was about to
serve the second pearl to Mark Antony, Lucius Plancus, who was refereeing the bet, stopped her and
declared Cleopatra the winner.
Gaius and Lucius Julius Caesar Vipsanius: They were Octavian’s grandsons, sons of his only daughter, Julia the Elder, who had married
his greatest friend and ally, Marcus Vipsanius Agrippa.
At birth their names were Gaius and Lucius Vipsanius Agrippa, but when Octavian adopted them as heirs in 17 BC, their names were changed to Gaius and Lucius Julius Caesar Vipsanius.
Water of the Tiber: Popes Clement VII, Paul III, and Gregory XIII drank it for their health (Gregory XIII and Paul III even had supplies of Tiber water brought along when they travelled). It is true though that the “acquaroli” or water-sellers loaded their water barrels upstream from the city.
The Mausoleum of Augustus: Octavian started building it, his sights already on greatness, perhaps somewhere around 30-28 BC, before he had been accorded the title of
Augustus (27 BC).
He intended it as a family tomb for the gens Julia, and modelled it on the royal “tumuli” of the ancient
Greek and Etruscan kings. This in itself was propaganda: the tomb recalled the legendary
antiquity and nobility of the Julian family.
Roman Brick Stamps: The practice of stamping fresh bricks with the name of the clay pit and owner of the brickworks started in the late
Republic. In addition, the stamp bore the date, by naming the consuls or the reigning emperor.
Below: A brick stamp on display at the Museum of Roman Civilisation (Museo della Civilità Romana).
Arval Brethren: The Fratres Arvales was an ancient priestly college, something like the Vestal Virgins. There were twelve priests who were consecrated to the Dea Dia, an agricultural and fertility goddess. Their role was to protect harvests, and they performed sacrifices to the goddess at her sacred grove outside of Rome on the right bank of the Tiber, which was found at Magliana Vecchia in the Vigna Ceccarelli. The college was declining by the late republic, but Octavian revived it; most subsequent emperors were members.
The Great Fire of 64: There were fires all the time
in ancient Rome. They broke out daily: wooden houses and open flames for cooking, heating, smelting and the like were an incendiary combination. Once fire broke out, it spread rapidly on the narrow streets, since the wooden houses
were built one up against the other. The towering Suburra Wall, whose fire-resistant gabine blocks protected the imperial fora,
is one of many signs that fires were frequent and destructive.
The famous cohortes vigilum were instituted by Octavian to fight fires.
Acca Larentia: She is part of the foundation myth. In the more widespread version, Faustulus, a shepherd, discovers the twins in the cave of the wolf,
and brings them home to his wife Acca Larentia, who raises them along with her twelve sons. The sons of
Acca Larentia and Faustulus are at the
origin of the Fratres Arvales, the Arval Brotherhood, a priestly college consisting of
twelve patricians. The myth says that one of Acca Larentia’s sons died, and Romulus took his
place, at which point he founded the college.
The Talking Statues of Rome: The practice of posting satirical epigrams or poems on statues in prominent public places (anonymously, in the nighttime hours) dates from the 16th century. The first statue to be used in this manner was a statue of Menelaos, which was soon called “Pasquino”, perhaps for a signatory, or perhaps for a teacher who was mocked in verses posted on the statue. When the pope, who was usually the butt of the joke, had Pasquino guarded at night, other statues around Rome started to talk. These are:
Basilicas: Early churches in Rome
took their layout not from temples, but from the public building known as a basilica (from Greek
basiliki stoa, literally “royal gallery”: the tribunal or judicial court) where business was
transacted and court cases were heard.
Below: Layout of a basilica. E: exedra
Sources for the Pantheon
The Pantheon: Belardi, Giovanni et al. Il Pantheon: Storia, Tecnica e Restauro. BetaGamma Editrice, copyright Sopraintendenza per i Beni Architettonici e per il Paesaggio di Roma, 2006.
Ziolkowski, A. “Pantheon”. In: Lexicon Topographicum Urbis Romae, Eva Margareta Steinby, editor. Edizioni Quasar, Rome. Volume 4, 1999. Pages 54-61.
Claridge, Amanda et al. Rome: An Oxford Archaeological Guide. Oxford University Press, Oxford, 1998. Pages 243-246.
Nero’s Baths: Martial, The Epigrams of Martial, text and translation by Henry George Bohn. G. Bell and Sons, London, 1904. Available online at: www.ccel.org: Martial, Epigrams. Book 7. Bohn’s Classical Library (1897).
Ghini, G. “Thermae Neronianae/Alexandrinae”, in : Lexicon Topographicum Urbis Romae, Eva Margareta Steinby (dir), Edizioni Quasar, Rome. Vol. 5, 1999. Pages 60-62 and illustrations.
Image Credits for the Pantheon
Photographs and drawings are the author’s unless otherwise indicated.
Arches of the Aqua Alexandrina: Photograph © Chris 73, 2009. Re-used under the terms of the creativecommons.org: Attribution-ShareAlike 3.0 Unported license. Original photograph on wikipedia: it.wikipedia.org: Aqua Alexandrina.