The Gier Aqueduct, including the loop in the Durèze Valley, is 86km long with a drop in level of only 105m, at an average gradient of 1.1m/km.
It crosses 21 communes, 11 in the Loire Department and 10 in the Rhône. Traces have been found at more than 250 sites. The current hypothesis for the date of its construction is the first half of the 2nd century AD.
Throughout its length the Aqueduct maintains roughly the same direction, towards the North-West. It is however possible to divide it into three parts: the first in the Gier Valley; the second on the Southern part of the Lyon Plateau; and the third ending up at Lyon after crossing the large Garon and Yzeron Valleys.