This structure, born from the recommendations made by Vauban to improve the Canal du Midi, was built in 1693. It is one of the most original structures on the Canal du Midi with its eleven-arched bridge. The function of this structure is to evacuate excess water from the canal to the Argent-Double River.
This evacuation is done in two ways. The first is by evacuating surface water by means of a spillway (overflow system) at the point where the bank is lowest at the level of the arches of the structure. The water that spills then falls in a cascade to the Argent-Double River below. After the surface water has been evacuated, the second means of evacuation of the structure is the spillway itself, that is to say, a bottom valve, which allows, with the action of man, to evacuate the water through the bottom. During maintenance work carried out in winter, this reach (portion between two locks) is emptied by this means.
A passage on the arches is built in order to maintain a "dry" continuity for the towing horses and avoid the slippery and perilous passage that this spillway presented. (Text from: La Redorte
and works of the Argent-Double)