Pont du Gard: The Roman Aqueduct Bridge of Nimes in France

The Pont du Gard is a Roman aqueduct bridge over the Gardon river in southern France, built in the mid-first century AD, probably around AD 40-60, to carry water across the valley to the Roman city of Nemausus, modern Nimes. Rising about 48.8 metres in three tiers of arches, it is the highest surviving Roman aqueduct bridge. It is a masterpiece of Roman engineering and one of France’s best-known ancient monuments.

Background: water for Nemausus

Nemausus was an important city in the Roman province of Gallia Narbonensis, in what is now southern France. It became a Roman colony under Augustus and grew rich, with a forum, temples such as the Maison Carree, an amphitheatre and city walls. Like many Roman cities, it wanted a large, steady supply of fresh running water for public fountains, baths and wealthy houses.

The local springs were not enough. Roman engineers chose the Fontaine d’Eure, a spring near Uzes about 20 kilometres north of Nimes in a straight line. Hills lay in between, so the aqueduct had to wind around them, giving a total length of about 50 kilometres. Like other Roman aqueducts, it worked by gravity alone, so the channel had to descend steadily from source to city.

The challenge was the very small difference in height. The whole aqueduct drops only about 12.6 metres over its length, an average of roughly 25 centimetres per kilometre. The deep valley of the Gardon lay on the route, and the engineers needed a bridge high enough to keep the channel on its gentle slope.

Construction and design

The Pont du Gard has three tiers of arches. The lowest has six arches, is about 142 metres long and about 22 metres high, and also served as a footbridge. The middle tier has 11 arches, is about 242 metres long and about 20 metres high. The top tier originally had 47 smaller arches, of which 35 survive, and is about 275 metres long. It carries the water channel, which was covered with stone slabs.

The bridge was built from yellowish limestone quarried nearby, much of it from a quarry at Estel, only a few hundred metres downstream. Builders used an estimated 50,000 tonnes of stone. Many blocks weigh several tonnes, the largest about 6 tonnes. The blocks of the arches were laid dry, without mortar, held in place by their precise fit and their weight.

Projecting stones and holes visible on the faces of the bridge supported the wooden scaffolding and centring, the curved wooden frames used to build each arch. Numbers and marks cut by the builders to show where blocks belonged can still be seen. The piers of the lower tier were given cutwaters, angled fronts that help the bridge resist the Gardon’s violent floods.

Over its whole length, the bridge itself drops only about 2.5 centimetres. The water channel on top was lined with waterproof mortar, and it was large enough for a person to walk through for maintenance.

Dating the bridge

For a long time the Pont du Gard was linked to Marcus Agrippa, Augustus’s general and son-in-law, who was in Gaul around 19 BC and was responsible for many water projects. This attribution appeared in many guidebooks.

From the 1980s, archaeologists excavated sections of the aqueduct and the distribution tank in Nimes. Coins, pottery and other finds in the construction layers suggested a later date, in the mid-first century AD, during the reigns of Claudius (41-54) or Nero (54-68). The dating to about AD 40-60 is now widely accepted, although precise years are not known. Construction of the whole aqueduct may have taken around 15 years.

How the aqueduct worked

Water reached Nimes at the castellum divisorium, a circular stone basin about 5.5 metres across. From there, 10 lead pipes carried water to different parts of the city. The tank was rediscovered in 1844 and can still be seen today. Modern estimates suggest the aqueduct carried roughly 30,000-40,000 cubic metres of water a day at its peak, a generous supply for a city whose population is usually estimated at several tens of thousands.

The water from the Eure spring was rich in dissolved limestone. Over time thick calcium deposits built up on the walls of the channel, narrowing it and slowing the flow. Maintenance seems to have declined from the fourth century, and the aqueduct probably stopped working completely by the early sixth century. Like the Aqueduct of Segovia in Spain, however, the bridge itself survived.

Myths and facts

A popular belief is that the Pont du Gard was built under Augustus by Agrippa. As explained above, the archaeological evidence now points to a date two or three generations later, although Agrippa’s name is still often attached to it.

Another common idea is that the whole aqueduct ran on high arches like the Pont du Gard. In fact most of its 50 kilometres ran underground or at ground level in a buried channel, following the contours of the land. Bridges such as the Pont du Gard were needed only where the route crossed valleys, and tunnels cut through some ridges.

Visitors also sometimes assume that the Romans used concrete or mortar throughout. The great arches are dry stone masonry, and their survival through nearly two thousand years of floods and neglect is a tribute to the precision of the stonework rather than to binding material.

Later history

After the aqueduct went out of use, the Pont du Gard continued to serve as a bridge. In the Middle Ages local lords charged tolls, and pieces of the second tier were cut back to widen the passage for travellers, which weakened the structure. The calcium deposits from the channel were also quarried as a building material.

In 1743-47 the engineer Henri Pitot built a road bridge alongside the lowest tier, which removed traffic from the ancient structure. In the mid-nineteenth century, after a visit by Napoleon III, major restoration work was carried out. The bridge withstood severe floods, including the great flood of September 2002, which damaged much of the surrounding area.

The Pont du Gard was added to the UNESCO World Heritage List in 1985. The site was later closed to road traffic and given a visitor centre and museum, and it now receives more than a million visitors a year.

By the numbers

Timeline

• c. 16 BC: Nemausus, already a Roman colony, receives new walls under Augustus.
• c. AD 40-60: The aqueduct and the Pont du Gard are built.
• 4th century: Maintenance declines and limestone deposits build up in the channel.
• Early 6th century: The aqueduct ceases to function.
• 1743-1747: Henri Pitot adds a road bridge beside the lower tier.
• 1844: The distribution tank in Nimes is rediscovered.
• 1985: The Pont du Gard is inscribed as a UNESCO World Heritage Site.
• 2002, September: The bridge survives a major flood of the Gardon.

Why it matters

The Pont du Gard shows the skill of Roman surveyors and builders, who carried water across a deep valley on a slope of a few centimetres while building to last for two thousand years. It is a symbol of how Rome transformed provincial cities and of the importance of water supply to Roman urban life.