Beaunant siphon bridge (Yzeron siphon)
Starting from the receiving reservoir at Plat de l’Air, Chaponost, the Yzeron siphon descends the hill to the Beaunant siphon-bridge in Sainte-Foy-lès-Lyon.
The Yzeron is the largest of the four siphons along the Gier Aqueduct and the siphon-bridge was the first part of the Aqueduct to be added to the list of Historic Monuments in 1875. The whole is an outstanding work of engineering..
Crossing the Yzeron was a real challenge at the time of its construction, almost 2,000 years ago: The Aqueduct had to cross a valley nearly 3km wide and about 140m deep.
The siphon bridge has some unique characteristics: 2660m long (between the two reservoirs) and a drop of 123m between the receiving reservoir and the siphon bridge. In order to cross a valley of this size and bring water to Lyon without the siphon would have needed a bridge as high as three Ponts du Gard piled on top of each other, which would have been impossible.
The presence of transversal arches, many of which are empty in the interior, is a unique feature, which makes the Beaunant siphon bridge something quite exceptional.
The foundations of the receiving reservoir of the siphon have been found (not visible) on the south side of Sainte-Foy-lès-Lyon.
The Aqueduct next crosses the Sainte-Foy-les-Lyon plateau in what is practically a straight line, alternating between underground sections and above-ground ones carried on walls or arches (rue de Narcel and rue Georges Clemenceau). It then crosses the parc du Brulet where part of the underground channel is visible.
The Aqueduct then arrives in Lyon.