Pont du Gard
The aqueduct carried water 50 kilometres to the city of Nemausus, present-day Nîmes, with a gradient of only a few centimetres per hundred metres. The bridge is 49 metres high in three tiers of arches, built without mortar. Projecting stones show where the scaffolding rested.
Nemausus was a flourishing Roman city in the province of Gallia Narbonensis, and as it grew it needed more water. The aqueduct was probably built around the middle of the 1st century AD; it was formerly attributed to Agrippa, but excavations have pointed to a somewhat later date. The water came from springs near Uzès and was carried in a channel that wound its way through the landscape. The most difficult obstacle was the valley of the river Gardon, and that is where the bridge was built. The stone was quarried in a limestone quarry close by. The blocks are large and were lifted with wooden cranes powered by treadwheels. Many stones bear carved marks and numerals indicating where they were to be placed. The work required precise surveying to maintain the even gradient.
The bridge has three tiers of round arches. The lowest has six large arches, of which the one spanning the river is the widest. The middle tier has eleven arches and the top tier a long row of smaller arches carrying the water channel itself. The arches of the two lower tiers are built of several parallel rings of stone side by side, not as a single wide vault. The channel was covered with stone slabs and sealed inside with mortar. Over time limescale built up on the inside of the channel, reducing the flow. The projecting stones and the small holes in the façade show where the scaffolding and wooden centring rested during construction; the stones were left in place for future repairs.
Maintenance ceased in late antiquity, and the aqueduct stopped working around the 6th century. The bridge survived because it gained a new role as a crossing over the river. In the Middle Ages the piers of the middle tier were cut back to make room for carts, which weakened the structure. In the 1740s a road bridge was built right against the lowest tier. Under Napoleon III a major restoration was carried out in the 1850s. The bridge has withstood several severe floods, including in 2002. The Pont du Gard early became a destination for travellers and artists and has contributed to the image of the Romans as unrivalled engineers. It became a World Heritage Site in 1985 and is today one of the most visited ancient monuments in France.