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Origin and history

The aqueduct tanks of Vallon d'Arche are remains of a Gallo-Roman hydraulic system located in Saint-Romain-au-Mont-d'Or, in the metropolis of Lyon. This work, integrated with the aqueduct of the Monts d'Or, captured the local waters to feed the ancient city of Lugdunum. This aqueduct, one of the four serving Lyons, is 26 km long and is characterized by its modestness and its reduced length compared to other similar infrastructures. Its route, partially underground, follows the level curves of the Gold Mountains, with sections still visible in several communes, including Saint-Romain-au-Mont-d'Or.

The aqueduct of the Monts d'Or, dated between 20 BC and 20 BC according to recent research, could have been initiated by Marcus Vipsanius Agrippa. It included works of art such as bridge-siphons, now missing, and looks for maintenance. At Saint-Romain-au-Mont-d'Or, the capture of the valley of Arches, still partially visible, fed the aqueduct via two galleries and two bunk rooms. This site, classified as a historic monument in 1991, is remarkable for its state of conservation and rarity among Roman aqueducts.

The hydraulic system of the Arches valley includes a superior chamber with distinct ancient elements (toil mortier, tegulae), while the lower chamber, though redesigned, remains functional. The water collected here today forms the stream of Vallon d'Arches, detached from the original aqueduct. According to Guy Jouvet's hypothesis, this capture could predate the extension of the aqueduct to Poleymieux-au-Mont-d'Or, explaining a local elevation of 4 meters. The complex, protected by a 50-metre strip in the Lyon PLUH, has been the subject of archaeological monitoring since 2013.

The aqueduct, little known because of the discretion of its remains, was studied in the 19th century by geologists such as Albert Falsan and Arnould Locard, who mapped its visible portions. Between 1991 and 2007, eight preventive archaeological operations took place along its supposed route. Although most remains have suffered from erosion, land movements or stone quarries, some sections, such as the Bois des Cieux section in Curis-au-Mont-d'Or, remain accessible. The theoretical flow of the aqueduct, estimated at between 2,000 and 15,000 m3/day according to the sources, still raises debate among historians.

Ranked a historic monument under the name of aqueduct tanks of Vallon d'Arche, this site is communal property and generally closed to the public, except during the European Heritage Days. Its interest lies in its rarity: it is the only catchment area visible among the Lyon aqueducts and one of the few intact examples of the Roman world. Recent excavations, such as those carried out between 2019 and 2020 near the Gambins in Poleymieux-au-Mont-d'Or, have confirmed the ancient origin of the work and refined the knowledge of its original layout.

The aqueduct of the Monts d'Or illustrates Roman ingenuity in water management, with a route adapted to topographical constraints. His ongoing study allows us to better understand the water supply of Lugdunum, capital of Gauls, and the construction techniques used during the Gallo-Roman era. The remains of Saint-Romain-au-Mont-d'Or, though partial, offer a valuable testimony of this hydraulic heritage, now protected and valued within the framework of the Metropolitan PLUH.

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