ture. In fact, the larger the curve of the arch, the
stronger the arch will be. In order to construct
such a form, and until the final stone at the top
of the arch (the “keystone”) has been placed, the
arch has to be supported by a system of scaffolding or “centering.” Once the keystone has been
positioned, however, the resulting form is much
stronger than the earlier arching techniques that
preceded it. (See Section I: Art Fundamentals for
a diagram outlining the various types and details
of vaulting systems.)
The Romans made many advances on the simple
arch as well. A series of arches butted up against
each other were used to create a barrel vault,
which could be taller and wider than a post-andlintel structure or a corbeled vault. Two barrel
vaults could be crossed at a ninety degree angle,
which resulted in a groin vault. This structure
transferred the thrust of the vault’s weight down
to freestanding piers, rather than solid walls,
which insured greater flexibility in terms of shaping space. This form would be the basis for many
important later innovations, and it was key to the
development of structures as sophisticated as
the Gothic cathedrals. [For a discussion of how
arches and the forces on them work, see http://
www.youtube.com/watch?v=CdNYTjXJPKE.]
Pont du Gard: Analysis
The Pont du Gard is an example of Roman archiBust of Roman statesman Marcus Agrippa.
tecture found at Nîmes (ancient Nemausus),
The Pont du Gard was long believed to
France. This example, far from the Italian penhave been built by Agrippa between
insula, shows the geographic breadth of the
20–16 bce, but recent excavations
Roman Empire. It also helps explain one aspect
suggest that it may actually have
of the Romans’ success and why they were able
been built in the first century ce.
to expand their reign so widely. As the Romans
conquered a new area, they did not simply force
the local population under their control. They were careful to provide positive advantages, such as
new construction projects like bridges and roads, in order to win the favor of the indigenous community. The Pont du Gard is a perfect instance of this. It is an aqueduct bridge built to bring clean water
to the people of Nîmes. The bridge transported clean water from springs at Uzès thirty-one miles away
and provided each of the approximately 50,000 citizens of the city with a hundred gallons per day.
The Pont du Gard and the aqueduct system for Nîmes were long believed to have been built by the
Roman statesman Marcus Agrippa between 20–16 bce. Recent excavations suggest that it may actually
have been built in the first century ce. Regardless of its true date of construction, the bridge is one of
the best preserved in the Roman world. As the water in the system traveled from the spring outside
the city, it was brought through an array of channels to the center of town. Simple gravity brought the
flow through these channels, which are set variously throughout the system, below ground, on low
walls, or across the bridge as seen here. Overall, the water fell only fifty-six feet from the elevation of
the spring to the fountains at Nîmes.
As the system reached the gorge of the Gardon River, it was necessary to construct a bridge. This
maintained the elevation of the channel and kept the water smoothly flowing through the system. The
resulting structure is the highest Roman aqueduct bridge constructed. It was designed as a threestory structure, 880 feet long and 160 feet high. Each of the large arches of the lower stories spans
eighty-two feet and is built of stone blocks weighing two tons each. No mortar or clamps were used
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