Last year, senior editor Michael Springer traveled through Europe visiting significant historic construction sites. This is the first in a series.
In the South of France near the city of Nîmes, a mythical structure has existed since the Romans erected it during the first century A.D. The Pont du Gard, or "bridge over the Gardon River," was built solely to transport water from a distant spring over the Gardon through a channel atop the span as part of a 31-mile-long aqueduct. But greater than its centuries of moving water, it has served as an attraction for a steady stream of visitors for two millennia, including tradesmen following their "Tour de France" to become finished journeymen (see "Rite of Passage," page 42). The marks they carved into the ancient stone can still be seen today.
To the Romans, a plentiful water supply defined civilization itself, and a constant supply of pure spring water defined a most luxurious existence. That cultural imperative was the reason this aqueduct wound through the countryside in an engineering feat that doused the citizenry of Nîmes with more than 500 gallons per person every day.
Roman workers toiled for 15 years laying the 11 million stones that enclosed the waterway and coating them with 31 miles of waterproof mortar. All the while, the slope had to be painstakingly controlled by the librator (topographical engineer) with bridges and tunnels, because the elevation drop between the spring in Uzès and the city of Nîmes was less than 40 feet. That's an average slope of .0029 inches per foot, less than three thousandths of an inch! A daunting surveying accomplishment even today, it is amazing that the engineers of the time were able to calculate a path that let gravity alone carry the water across the landscape while adding many miles to the aqueduct's length to avoid insurmountable obstacles. The straight-line distance between each end is only about 12 miles.
The Pont du Gard was the centerpiece of the aqueduct and is one of the few recognizable parts still standing. Built sometime between 38 and 52 A.D., this is the tallest structure of its type built by the Romans, towering an impressive 160 feet above the river and featuring the widest single Roman arch ever built, spanning the river's normal flow at more than 80 feet. The overall length of the span was more than 1,600 feet across, over which the canal on the top level slopes only 3/8 inch in elevation. An estimated 1,000 men labored for three to five years on this structure using more than 55,000 tons of stone. This Herculean project required the talents of stonecutters, masons, blacksmiths, carpenters, lime burners, and an army of helpers. In fact, the workforce was largely supplied and organized by the military utilizing local craftsmen, soldiers, mercenaries, and slaves.