10-50Restored cutaway view (left) and lateral section (right) of the Pantheon, Rome, Italy, 118–125 ce(John Burge).
The Pantheon’s traditional facade masked its revolutionary cylindrical drum and its huge hemispherical dome. The interior symbolized both the orb
of the earth and the vault of the heavens.
268 Chapter 10 THE ROMAN EMPIRE
influential designs in architectural history. The Pantheon reveals the
full potential of concrete, both as a building material and as a means
for shaping architectural space. Originally, visitors approached the
Pantheon from a columnar courtyard, and the temple itself, like
temples in Roman forums, stood at one narrow end of the enclosure
(FIG. 10-50,left). Its facade of eight Corinthian columns—almost
all that could be seen from ground level in antiquity—was a bow to
tradition. Everything else about the Pantheon was revolutionary.
Behind the columnar porch is an immense concrete cylinder covered
by a huge hemispherical dome 142 feet in diameter. The dome’s top
is also 142 feet from the floor (FIG. 10-50,right). The design is thus
based on the intersection of two circles (one horizontal, the other
vertical) so that the interior space can be imagined as the orb of the
earth and the dome as the vault of the heavens.
If the Pantheon’s design is simplicity itself, executing that design
required all the ingenuity of Hadrian’s engineers. They built up the
cylindrical drum level by level using concrete of varied composition.
Extremely hard and durable basalt went into the mix for the founda-
tions, and the builders gradually modified the “recipe” until, at the
top, featherweight pumice replaced stones to lighten the load. The
dome’s thickness also decreases as it nears the oculus, the circular
opening 30 feet in diameter that is the only light source for the inte-
rior (FIG. 10-51). The use ofcoffers (sunken decorative panels) less-
ened the dome’s weight without weakening its structure. The coffers
further reduced the dome’s mass and also provided a handsome pat-
tern of squares within the vast circle. Renaissance drawings suggest
that each coffer once had a glistening gilded-bronze rosette at its
center, enhancing the symbolism of the dome as the starry heavens.
Below the dome, much of the original marble veneer of the
walls, niches, and floor has survived. In the Pantheon, visitors can get
a sense, as almost nowhere else, of how magnificent the interiors of
Roman concrete buildings could be. But despite the luxurious skin of
the Pantheon’s interior, the sense experienced on first entering the
structure is not the weight of the enclosing walls but the space they
enclose. In pre-Roman architecture, the form of the enclosed space
was determined by the placement of the solids, which did not so
much shape space as interrupt it. Roman architects were the first to
conceive of architecture in terms of units of space that could be
0 7550 1 00 feet
0 15 30 meters10-51Interior of the Pantheon, Rome, Italy, 118–125 ce.
The coffered dome of the Pantheon is 142 feet in diameter and 142 feet
high. The light entering through its oculus forms a circular beam that
moves across the dome as the sun moves across the sky.