The Pont du Gard is the highest of all elevated Roman aqueducts, and, along with the Aqueduct of Segovia, one of the best preserved. It was added to UNESCO's list of World Heritage Sites in 1985 because of its historical importance.
The aqueduct bridge is part of the Nîmes aqueduct, a 50-kilometre (31 mi) system built in the first century AD to carry water from a spring at Uzès to the Roman colony of Nemausus (Nîmes). Because of the uneven terrain between the two points, the mostly underground aqueduct followed a long, winding route that called for a bridge across the gorge of the Gardon River.
The bridge has three tiers of arches, stands 48.8 m (160 ft) high, and descends a mere 2.5 centimetres (1 in) – a gradient of only 1 in 18,241 – while the whole aqueduct descends in height by only 17 m (56 ft) over its entire length, which is indicative of the great precision that Roman engineers were able to achieve, using simple technology. The aqueduct formerly carried an estimated 200,000 m3 (44,000,000 imp gal) of water a day to the fountains, baths and homes of the citizens of Nîmes. It may have been in use as late as the 6th century, with some parts used for significantly longer, but a lack of maintenance after the 4th century led to clogging by mineral deposits and debris that eventually choked off the flow of water.
After the Roman Empire collapsed and the aqueduct fell into disuse, the Pont du Gard remained largely intact, due to the importance of its secondary function, as a toll bridge. For centuries the local lords and bishops were responsible for its upkeep, in exchange for the right to levy tolls on travellers using it to cross the river, although some of its stones were looted and serious damage was inflicted on it in the 17th century. It attracted increasing attention starting in the 18th century, and became an important tourist destination.
It underwent a series of renovations between the 18th and 21st centuries, commissioned by the local authorities and the French state, that culminated in 2000 with the opening of a new visitor centre and the removal of traffic and buildings from the bridge and the area immediately around it. Today it is one of France's most popular tourist attractions, and has attracted the attention of a succession of literary and artistic visitors.