A Roman aqueduct
across the Gard River
, in southern France
. It is the largest
and best preserved Roman bridgework still in existence
It was built in 19 B.C., by Agrippa, to supply the new colonia of Nîmes with water, and as a bridge large enough to carry chariots across the waterway. It carried water from a spring nearly 30 miles away, to supplement the small aquifer within the growing town itself. Much of its run is underground, with a descending ratio of 1 foot for every 3000 feet of its length.
The most impressive feat of engineering is the span over the river. It consists of three tiers of arches and is 900 feet long and 160 feet high. Each arch was designed in such a way as to require only one wooden beam for support during its construction, and no cement is used in any part of the masonry.
This famous construction is admired for its architectural proportions and longevity. The lowest tier has been used as a road bridge since the 18th century.