Pont du Gard Roman Aqueduct

The Pont du Gard is a Roman Aqueduct built to provide a water source for Nimes (Nemausus).
It is one of the top five French Tourist Attractions and has been a Unesco World Heritage Site since 1985.

It was built by the Roman General Agrippa after being ordered by Augustus in 19 BCE.
It took 35 years to build and was completed in 14 CE.
In the 1620’s Henri Duke of Rohan reduced the thickness of the pillars on the middle level by one third, to create a road to convey carts and cannons, so that he could move his artillery to combat the Huguenots. Despite this reconstruction, the viaduct still stands today.

The nearest Source was at Uzes, 13 miles (21km) north as the crow flies.
But this meant tunneling through the mountains called the Garrigues de Nimes.
Consequently the route had to go round the mountains, a 31 mile (50 km) route, and over the 160 foot (48m) deep gorge of the River Gard.
The height difference between the source and Nimes was only 55 ft (17m).
The Gradient is 1 in 3000. This was close to the minimum gradient needed to allow water to flow for the whole route.
The water flowed through a cement lined channel. This had to be regularly cleaned to prevent silting up which it did after the Fall of the roman Empire having up to 20 inches (50cm) of material on each wall of the conduit.
It carried an estimated 200,000 cubic metres of water per day to Nimes.

The height required over the River was 160 ft (48m) making this the highest Aqueduct in the Roman Empire.
To achieve this, three bridges were built, one on top of the other.
A wooden framework of aches was constructed, and the stones positioned over the framework.
Stones were raised into position by cranes.
The Roman Crane was operated by men walking on the spot in a timber treadwheel, which operated a winding drum connected by a rope to a large wooden arm.
Some stone blocks weighed up to 6 tons each.
No mortar or iron clamps were used, the stones all fitted perfectly into the arches, which are three blocks thick.
The Lowest Level has 6 Arches, the Middle Level 11 Arches and the Upper Level has 35 Arches (12 have been lost over time).

Photo and map: Pont du Gard, Nimes