After the Roman Empire collapsed and the aqueduct fell into disuse, the Pont du Gard remained largely intact with a secondary function as a toll bridge.

A series of renovations between the 18th and 21st centuries, commissioned by local authorities and the French state, culminated in 2000 with opening of a new visitor centre and removal of traffic and buildings from the bridge and area immediately around it.

[5] The Nîmes aqueduct was built to channel water from the springs of the Fontaine d'Eure near Uzès to the castellum divisorum (repartition basin) in Nemausus.

In one section, the winding route between the Pont du Gard and St Bonnet required an extraordinary degree of accuracy from the Roman engineers, who had to allow for a fall of only 7 millimetres (0.28 in) per 100 metres (330 ft) of the conduit.

When it was excavated, traces of a tiled roof, Corinthian columns and a fresco decorated with fish and dolphins were discovered in a fragmentary condition.

As well as obstructing the flow of the water, dangling roots introduced algae and bacteria that decomposed in a process called biolithogenesis, producing concretions within the conduit.

It required constant maintenance by circitores, workers responsible for the aqueduct's upkeep, who crawled along the conduit scrubbing the walls clean and removing any vegetation.

Some substantial remains of the above-ground works can still be seen today, such as the so-called "Pont Rue" that stretches for hundreds of metres around Vers and still stands up to 7.5 m (25 ft) high.

A surveyor or mensor planned the route using a groma for sighting, the chorobates for levelling, and a set of measuring poles five or ten Roman feet long.

The builders may have used templates to guide them with tasks that required a high degree of precision, such as carving the standardised blocks from which the water conduit was constructed.

[22] The aqueduct as a whole would have been a very expensive undertaking; Émile Espérandieu estimated the cost to be over 30 million sesterces,[31][32] equivalent to 50 years' pay for 500 new recruits in a Roman legion.

It was painted with olive oil and covered with maltha, a mixture of slaked lime, pork grease and the viscous juice of unripe figs.

[33] Although the Pont du Gard is renowned for its appearance, its design is not optimal as the technique of stacking arches on top of each other is clumsy and inefficient (and therefore expensive) in the amount of materials it requires.

The Acueducto de los Milagros in Mérida, Spain and the Chabet Ilelouine aqueduct bridge, near Cherchell, Algeria[34] utilise tall, slender piers, constructed from top to bottom with concrete-faced masonry and brick.

[35] The construction of the aqueduct has long been credited to the Roman emperor Augustus's son-in-law and aide, Marcus Vipsanius Agrippa, around the year 19 BC.

[39] However, it suffered serious damage during the 1620s when Henri, Duke of Rohan made use of the bridge to transport his artillery during the wars between the French royalists and the Huguenots, whom he led.

To make space for his artillery to cross the bridge, the duke had one side of the second row of arches cut away to a depth of about one-third of their original thickness.

[41] In 1703 the local authorities renovated the Pont du Gard to repair cracks, fill in ruts and replace the stones lost in the previous century.

[11][41] The novelist Alexandre Dumas was strongly critical of the construction of the new bridge, commenting that "it was reserved for the eighteenth century to dishonour a monument which the barbarians of the fifth had not dared to destroy.

"[42] The Pont du Gard continued to deteriorate and by the time Prosper Mérimée saw it in 1835 it was at serious risk of collapse from erosion and the loss of stonework.

The work involved substantial renovations that included replacing the eroded stone, infilling some of the piers with concrete to aid stability and improving drainage by separating the bridge from the aqueduct.

From the 18th century onwards, particularly after the construction of the new road bridge, it became a famous staging-post for travellers on the Grand Tour and became increasingly renowned as an object of historical importance and French national pride.

[46] In 1786 his great-great-great-grandson Louis XVI commissioned the artist Hubert Robert to produce a set of paintings of Roman ruins of southern France to hang in the king's new dining room at the Palace of Fontainebleau, including a picture depicting the Pont du Gard in an idealised landscape.

[47] Napoleon III, in the mid-19th century, consciously identified with Augustus and accorded great respect to Roman antiquities; his patronage of the bridge's restoration in the 1850s was essential to its survival.

[49] In 1996 the General Council of the Gard département began a major four-year project to improve the area, sponsored by the French government, in conjunction with local sources, UNESCO and the EU.

The redevelopment has ensured that the area around the Pont du Gard is now much quieter due to the removal of vehicle traffic, and the new museum provides a much improved historical context for visitors.

The sight of this simple and noble work struck me all the more since it is in the middle of a wilderness where silence and solitude render the object more striking and the admiration more lively; for this so-called bridge was only an aqueduct.

"[53]The novelist Henry James, visiting in 1884, was similarly impressed; he described the Pont du Gard as "unspeakably imposing, and nothing could well be more Roman."

[54]The mid-19th-century writer Joseph Méry wrote in his 1853 book Les Nuits italiennes, contes nocturnes that on seeing the Pont du Gard: [O]ne is struck dumb with astonishment; you are walking in a desert where nothing reminds you of man; cultivation has disappeared; there are ravines, heaths, blocks of rock, clusters of rushes, oaks, massed together, a stream which flows by a melancholy strand, wild mountains, a silence like that of Thebaid, and in the midst of this landscape springs up the most magnificent object that civilization has created for the glory of the fine arts.

A man, suffering from the unrest of our time, might do worse than camp out for three days, fishing and bathing under the shadow of the Pont du Gard.