Malpas Tunnel

The Malpas tunnel carries the Canal du Midi under the d'Ensérune hill in Hérault, France. Excavated in 1679, it was Europe's first navigable canal tunnel and is a monument to the determination of Pierre-Paul Riquet, the chief engineer. It is located in the commune of Nissan-lez-Ensérune near to the archaeological site Oppidum d'Ensérune. There was great disappointment when the works reached the hill d'Ensérune. A few metres of digging in hard rock revealed a very brittle sandstone subject to slippage. Colbert, the prime minister, halted the works when he was made aware of the situation. The portal was blocked and the workings re-sited. Riquet's detractors took advantage of this situation to impede the project. Colbert announced that he would send royal commissioners to decide the canal's future. The advice of the Chevalier de Clerville, architect to Louis XIV, was to cross the river Aude rather than tunnel through the hill.