It is unique in its construction, as well as being the highest aqueduct to be built in the Roman Empire. Situated 20km from Avignon and 23km from Nîmes, it has been a Unesco World Heritage Site since 1985 and it is the most-visited Roman site in the country.
The Roman architectural marvel
The bridge was built by the Romans in around 50AD and was the centrepiece of an astonishing aqueduct which took running water to what is now Nîmes for around three centuries.
It fed the fountains installed in every street, the spas, gardens and private homes.
Nemausus, as Nîmes was called at the time, was one of the major Roman cities in France, with an estimated 20,000 inhabitants. It had all the characteristics of a modern town, with a forum and temple, but although water was available from wells and rainwater, it was not abundant, and the population was growing.
To give the city real status, it needed flowing fountains in its gardens and the ability to change the water frequently in its public baths.
There are no records of who came up with the idea of an aqueduct, nor of who financed it, and no one knows who the architects and engineers of this extraordinary structure were, but it is likely the experts came from Rome, where they already knew how to build aqueducts.
Built with slave labour
It is estimated the bridge took five years to build and the whole aqueduct, from source to city, took 15 years.
Around 500 workers were taken on to build the Pont du Gard, and the same number again for the rest of the aqueduct. Some were paid, but slaves were also used, not just for the manual labour but for skilled work such as shaping the stone.
First, the pillars on the bottom bridge were built, followed by the arch and then the top, and this process continued up each of the levels. Wooden scaffolding was used, built by skilled carpenters. There were also cranes, powered by slaves walking within a treadwheel, which drove the hoisting and lowering device, capable of lifting huge blocks of stone.
It is thought the aqueduct worked until 500AD. However, it is likely it took water to Nemausus for only around 300 years, after which the city’s importance dwindled and, with it, its population.
Keeping the water flowing freely required a lot of maintenance work to clear the limestone deposits which built up. This was a physical job, no doubt carried out by teams employed by the city, and which would have come to an end with the decline of Nemausus.
The water which still ran through the aqueduct for the next 200 years was probably used by farmers for irrigation.
Transformation into a historic monument
By the Middle Ages, however, the structure was no longer in use and people pilfered stone from it for their own building projects.
Though the aqueduct was never designed as a road, people began using it to cross the river in about the 11th century. They hacked away stone from the pillars on the first level to make it wide enough to take a horse and cart.
A toll was charged for crossing the bridge, making it a valuable source of income. Otherwise, it might have been entirely dismantled over time for its stone.
Much later, in 1743, a parallel bridge was built, which could take more traffic.
It was only in the 19th century that the intrinsic value of ancient monuments began to be appreciated.
In 1840, Prosper Mérimée, the first inspector of historic monuments, listed the Pont du Gard as one of the most important structures in France, meaning its future was assured and the pillars were restored.
From the 20th century, the bridge started attracting thousands of tourists. The parallel bridge was closed to traffic and, in 2000, the site was revamped to better accommodate tourism, while preserving the bridge and the local environment.
There is now a museum showing how it was built, and it is also possible to book a guided tour along the canal at the top of the bridge.
The first small section is open to the sky but most is in a tunnel, as the waterway was covered along its whole length to protect it.