The Languedoc Canal, or Canal du Midi, marked a milestone in the development of long distance canals in Europe. Built between 1666 and 1681, it links the Atlantic and the Mediterranean, running 240km from the River Garonne at Toulouse via Carcassonne to Beziers.
It was a vital transport link for wine exporters in south west France and Provence. They used the canal to ship their produce to Bordeaux, one of France's main west coast trading ports. It is still in use today, although at 15m wide and 2.4m deep, it is too small to accommodate large modern freight barges. Instead it is mainly used by tourist traffic.
The scale of the project inspired 18th century author Voltaire to praise it as the 'most glorious monument' to its patron King Louis XIV, who had a penchant for grands projets like the Louvre and the Chateau de Versailles. Former ICE Vice President Alec Skempton goes further, describing it as 'the greatest feat of civil engineering in Europe between Roman times and the 19th century'.
In terms of size the Canal du Midi was an undertaking on a scale comparable with the mega schemes of the 1980s. Apart from its great length it has 100 locks leading up to the watershed 62m above sea level. At the peak of construction in 1669 more than 8,000 labourers were at work on the canal, which was split into 12 construction sections.
Such was the excitement generated by the project that tourists came to see the work and contemporary poets celebrated Colbert, the project's lead engineer.
Construction was not without its problems. The walls of one of the first locks collapsed soon after it was built, forcing a major redesign of it and others. New designs reduced the height of the lock walls by 30% and introduced curves into the walls to strengthen them against earth pressure.
Locks were only one of the engineering challenges. The canal also passes through a 162m tunnel at Malpas near Beziers and crosses the rivers in its path on large masonry aqueducts.
One of the main tasks was construction of the water supply link to feed the canal at the watershed. This is effectively a mini canal transporting water more than 19km between two mountain streams before branching off into another 30km channel feeding into a 5Mm3 reservoir behind a purpose built 31.5m high earth filled dam close to the canal.