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Heritage classified

Key figures

Origin and history

The Naurouze basin, located in Montferrand, Aude, is a key element of the Canal du Midi, built in the 17th century under Louis XIV. This octagonal reservoir, designed by engineer Pierre-Paul Riquet, marks the highest point of the canal (194 m above sea level), on the water divide between the Atlantic Ocean and the Mediterranean. It provides continuous power to the sharing bay, a section of 5.19 km between the locks of the Ocean and the Mediterranean. Riquet had imagined an ideal city, with pavilions inspired by Place Royale in Paris, but only the basin and its hydraulic infrastructures were realized.

The site is based on an ingenious water collection system: the plain channel (38 km), fed by the lake of Saint-Ferréol (Montagne Noire), carries water to the basin. This one, described in 1697 as "the most beautiful in the world" by cartographer J.B. Nolin, is 400 m long by 300 m wide, with a constant depth of 3 m. Sparrows (Marteillere, Naurouze) regulate surpluses, while a historic pumping station, milling plant and engineering housing complete the whole. Lobelisque erected in 1825 by the heirs of Riquet commemorates his genius, with the inscription: "To Pierre-Paul Riquet, Baron of Bonrepos, author of the Canal des Deux Mers en Languedoc".

The threshold of Naurouze, known since Antiquity as the Gallic isthmus, was already a strategic passage on the Roman Via Aquitania from Narbonne to Toulouse. Riquet was at the heart of his project by focusing on the technical challenges: permanent water supply, vertical management, and the creation of a junction between the two sides of the canal. The work began in 1667 with the Toulouse-Naurouze section, completed in 1672. The canal was fully completed in 1682 after adjustments. The octagonal basin, originally planned as the centre of an ideal city, was finally abandoned to the benefit of an excavated divide, and the locks of the Ocean and the Mediterranean were moved.

Ranked a historic monument in 1996, the site now includes the basin (partly sanded), the obelisk, and the remains of hydraulic infrastructure. The peripheral channel, visible, still traces the original octagonal shape. The place symbolizes both the civil engineering of the modern era and Riquet's ambition, which dreamed of unifying the seas by a waterway, while irrigating the agricultural land of Lauragais. The 30 million m3 of water passing through the site annually testify to the sustainability of its system, still in operation after more than three centuries.

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