63 locks operate along the 149 miles (240 km) of the course of the Canal du Midi that runs from the Garonne to Sète and the Étang de Thau. Among these, the Douce is a single-chamber lock built around 1674 about a hundred kilometers from Toulouse at an altitude of 357.61 ft (109 m). Located in the town of Carcassonne in the Aude department, it is adjacent to the locks of Herminis to the west and Carcassonne to the east.