The 9 Écluses (nine locks) of Fonseranes are among the spectacular sites on the course of the Canal du Midi. This eightfold made up of eight locks and nine pools in a row allows boats to overcome a total height difference of 69 ft (21.50 m). The oval basins of the locks allow the stone walls to better resist the pressure of the water flowing into them. This shape is, therefore, the norm in all the locks of the Canal du Midi. Right next to the locks, the water slope allows the passage of out of gauge barges that cannot cross the basins of the 9 Écluses. However, this invention was little used in Fonseranes, where commercial traffic was already in sharp decline shortly after the completion of the work.