ground floor was improved and the surroundings enhanced by additional trees.

See also

Archigram; Renault Parts Distribution Center

Further reading

Bragstad, Jeremiah O., and Ivan Zaknic. 1983. Pompidou Center. Paris: Flammarion.

Silver, Nathan. 1994. The Making of Beaubourg: A Building Biography of the Centre Pompidou, Paris. Cambridge, MA: MIT Press.

Pont du Gard

Nîmes, France

The highest aqueduct the Romans ever built, described as “the most daring construction” of its day, supplied the provincial town of Nemausus (modern Nîmes) in Gaul (France). It delivered daily an estimated 44 million gallons (200 million liters) that were distributed through ten mains to the city’s baths, fountains, public buildings, and houses. The most spectacular part of it is now known as the Pont du Gard. The description on the UNESCO World Heritage List of this remarkable feat of engineering reads: “The hydraulic engineers and … architects who conceived this bridge created a technical as well as artistic masterpiece.”

Aqueducts had been employed more than two millennia earlier in the cities of the Indus valley and Mesopotamia, but the extensive systems that the Romans constructed both at home and abroad were the most sophisticated in the ancient world. The earliest, the Aqua Appia, was a 10-mile (16-kilometer) underground conduit built to serve the city of Rome in about 310 b.c. The Aqua Marcian, built 150 years later, carried water 56 miles (90 kilometers) to the capital; for about a fifth of its length it was supported on arches above the ground. Altogether, ancient Rome was supplied by eleven aqueducts, delivering an estimated 350 million gallons (1.6 billion liters) daily.

By the end of the first century b.c. Nemausus had become a key Roman settlement with a growing population, thought to be close to 50,000. Its water supply was inadequate, and following a visit by the emperor Augustus’s son-in-law Agrippa in 19 b.c., plans were put in hand to bring water about 30 miles (50 kilometers) from the Fontaine d’Eure springs at Uzès to a stone reservoir near the city. The aqueduct was probably completed during the reign of Trajan (a.d. 98–117); it took over eighty years to build. In all Roman aqueducts, water flowed from source to destination under gravity, so the scale of the project was daunting—mountains had to be tunneled, hollows filled and valleys crossed—and a high degree of precision also was critical: the Uzès spring stood only 57 feet (17 meters) above the reservoir, and the 12-mile (20-kilometer) direct route between them called for 30 miles (50 kilometers) of aqueduct winding through the hilly region. The average gradient was a mere 1 in 3,000; in some places it was as gentle as 1 in 20,000. It was made steeper just before it reached the Gardon Valley, in order to reduce the height of the awesome Pont du Gard across the river about 11 miles (18 kilometers) northeast of Nîmes.

The massive 155-foot-high (47.2-meter) three-tiered bridge spans 920 feet (275 meters) across the valley. It was constructed of locally quarried limestone, finely dressed into ashlar blocks, some weighing up to six tons. The lower two tiers are laid without mortar, the blocks being secured with iron clamps. The 473-foot-long (142-meter) bottom tier has six irregular voussoir arches, 73 feet (22 meters) high, set out to span between stable rock outcrops in the riverbed. The middle tier has eleven 67-foot -high (20-meter) arches; spanning just over 800 feet (242 meters), it carries a 23-foot-high (7-meter), 35-arch arcade that supports the specus, a covered rectangular water channel about three feet (1 meter) wide and 6 feet high. That the Romans considered the structure to be utilitarian and “ordinary” is evidenced by the projecting blocks that nobody bothered to dress after the centering that they supported was removed.

The bridge has proven to be extraordinarily strong. Despite the Gardon River being “one of the most treacherous and rapid” in France, the Pont du Gard has resisted its onslaught for two millennia. Sheer mass—the weight of stone has been estimated at 16,000 tons (14,500 tonnes)—is one reason for that, and another is the combined skills of the engineers who designed it and the masons who built it. Moreover,