Pont du Gard

November 17, 2009

Since July, I’ve been living in the South of France, exploring the local culture, geography and historic marvels.  Periodically, I’ve been sharing some of the interesting engineering-related stories that I’ve uncovered.  You can read about more of my ongoing adventures at http://mistralwriter.blogspot.com

Even in these technologically advanced times, the massive Roman structures of the first century impress. Perhaps the Romans‘ most astounding feats were related to their ability to move water. The Pont du Gard brought fresh spring water nearly 50km from northern highlands to the Roman city at Nîmes. On the way the ancient engineers had to build a 275m long bridge over the Gardon River.

The Pont du Gard is comprised of 56 stone arches. The six lower arches are most impressive, 22m high and 6m thick. Making the story of its engineering even more incredible is the fact that it was constructed without the use of mortar. The precise site surveying and construction sequencing were also feats for the ancient world. Remnants of the shoring system can still be seen in the form of stone corbels protruding from the face of the arches. It’s amazing to think that block and tackle could be used to lift stones weighing up to six tons. Nevertheless, it’s estimated that the Pont du Gard was erected in 3 years, employing up to 1,000 workers.

In the middle ages, the Pont du Gard served as a pedestrian bridge across the river. At one point in history, the middle level of arches were chiseled back to provide a wider platform for horse cart traffic. Fortunately, the bridge has survived that defacement, centuries of forceful river surges and local seismic activity.

Hundreds of thousands of visitors now cross by the Pont each year on a more modern stone bridge designed to match the Roman architecture.  Most people don’t realize that they’re not actually walking across the Pont du Gard.  However, on special occasions it is possible to walk through the uppermost passage that carried the Roman water channel.  Only a few people are allowed to cross at a time, likely an evacuation precaution.  Surely the weight of the stone bridge itself dwarfs the handful of people that can fit within.  The experience is worth the substantial wait.

The Pont du Gard is an amazing structure. Standing in it’s presence, one reflects on the permanence of construction. How will structures built today age? Will they seem as elegant to our progeny 2000 years from now? The Romans were building an eternal empire; what are we building for?

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