Aqueduct of the Gier

The Aqueduct of the Gier (French Aqueduc du Gier) is an ancient Roman aqueduct probably constructed in the 1st century AD to provide water for Lugdunum (Lyon), in what is now eastern France. It is the longest and best preserved of four Roman aqueducts that served the growing capital of the Roman province of Gallia Lugdunensis. It drew its water from the source of the Gier, a small tributary of the Rhone, on the slopes of Mont Pilat, 42 km (26 mi) south-west of Lyon. Following a sinuous path, at 85 km (53 mi) the aqueduct of the Gier is the longest known of the Roman aqueducts. Its route has been retraced in detail, following the numerous remains. Leaving the uplands of the Massif du Pilat, department of the Loire, the aqueduct hugs the surface relief and crosses the department of the Rhone, passing through Mornant, Orliénas, Chaponost and Sainte-Foy-lès-Lyon to terminate at Lyon. In its extent, it draws upon the whole repertory of Roman techniques of aqueduct building, taking a slope that averages 0.1%, or a meter every kilometer. There are 73 km (45 mi) of covered ditches laid with a concrete culvert 3 m (9.8 ft) high and 1.5 m (4.9 ft) wide, which is sunk as deep as 4 m (13 ft) beneath the land surface.