Aqueduct of the Gier

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.

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.

Four inverted siphon tunnels cross the particularly deep and wide river valleys of the Durèze, the Garon,[4] the Yzeron and the Trion on pipe bridges raised on high arches.

From the castellum water was carried, now pressurized, in a set of airtight lead pipes laid side by side, with soldered joints, down the valley slope, across a bridge spanning the river—whose piers and arches are the most notable remains of the system—and up the facing slope, to a tank slightly lower than the head tank, losing just a little hydraulic head in the process.

[7] In addition he notes that a recently excavated public fountain on the hill of Fourvières, datable about 50 AD could not have been supplied with water until the Giers aqueduct was complete.