At a place called 'Le Malpas' (meaning 'bad passage' in Occitan dialect), the Canal du Midi crosses a hill that separates the Aude and Orb valleys. For the canal to pass through this hilly area, Pierre-Paul Riquet needed to dig out a 160-m-long tunnel. This is the oldest navigation tunnel in Europe. The building work was carried out between 1679 and 1680 and was one of Riquet's most notable achievements.
The Canal du Midi route was a topic of heated debate throughout the whole construction process.
After Argens-Minervois, the first idea was to head down towards Vendres lake, north-east of Narbonne and then on to Béziers, Agde and Thau lagoon along the coast. But Riquet was not a fan of this option because the high water levels on the Aude river could pose a threat to the canal. His proposal was to head straight for Béziers at a steady altitude from Argens to Fonseranes.
That way, the canal would stay away from the raging waters of the river, but there was another challenge to face. At Ensérune mountain, there was a hill in the way. Pierre-Paul Riquet chose to pass the canal under this hill, by digging out a tunnel at the Col du Malpas.
He knew this idea was possible because there was already an aqueduct dating from the Middle Ages in this rock, used to drain the water from Montady lake, a natural body of water north of Ensérune mountain, towards Capestang wetlands further south.
But there were disadvantages in opting for this route because it would mean the canal wouldn't pass through Narbonne, a key city in the terms of the political and economic interests of Languedoc in the 17th century. Also, in summer 1679, when the labourers responsible for digging out the canal arrived in front of the hill, they accused Riquet of making a huge mistake in thinking the canal could be passed through this sandy mountain. Jean-Baptiste Colbert, King Louis XIV's controller-general of finances, was notified of the situation and suspended the construction work. The entire project was under threat. Jean-Baptiste Colbert announced a visit from the Royal commissioners to decide upon the future of the canal.
Pierre-Paul Riquet did not follow Jean-Baptiste Colbert's orders and decided to commence digging into the hill.
He asked Pascal de Nissan, who was in charge of maintenance work for Montady aqueduct at the time and whom he had complete faith in, to put together a small team of labourers to secretly go ahead with the work.
It is believed that in the space of 7 days, the team created a small passage measuring 1.30 metres in width and almost 2 metres in height. When the commissioners arrived, Riquet took them into the passage with torches. They admitted that his idea was a legitimate one.
When Colbert heard of this, he authorised construction work to be resumed. In autumn 1679, Pierre-Paul Riquet entrusted Pascal de Nissan with the management of the project, which was proving to be quite complicated. Riquet kept a very close eye on the work. The construction work on Malpas tunnel and two channels, one upstream and one downstream, was completed in summer 1680.
This was the last significant engineering structure of Pierre-Paul Riquet's career, as he died on 1 October 1680.
A few years after it was opened to navigation, the tunnel needed reinforcing on the lower third of the structure, because the tufa stone they had dug into had become fragile.
Work had to be carried out in several stages, between 1695 and 1720, to build a new stone arch. The other two thirds of the structure did not require any modifications.
The erosion on this soft rock inside the tunnel has created a beautiful visual effect.
The Malpas passage is 173 metres long altogether, and 85 metres are inside the tunnel.
In the tunnel, the canal is 7 metres wide and 8.5 metres high. There is a 1-metre-wide towpath so that one or more men can pull barges along through the tunnel, while the horses pass around the tunnel.
This was the first navigation tunnel to be built in Europe. Cardinal Bonzi, archbishop of Narbonne, compared it to the Pausilippe passage which is a road dating back to Antiquity between Naples and Pozzuoli!
In the 17th and 18th centuries, the word tunnel was never used to describe this structure, which was known as a 'voûte' meaning 'archway' or sometimes even a 'grotte', meaning cave.
The word tunnel is an English word derived from the French word 'tonnelle', which describes the curved shape of a barrel. When a great number of tunnels were built for the railroad network, the word 'tunnel' replaced the others.
Le Malpas © Caroline Brandt
The Col du Malpas is also well-known for the other routes and tunnels that pass through at varying levels. It is believed that the ancient Via Augusta route probably passed through here, as well as the Roman Via Domitia route.
Under the navigation tunnel, barely 1 metre below the canal, the railroad between Narbonne and Béziers, built in 1855-1856 also passes through here. If you are in Malpas tunnel at the same time as a train, you'll hear the muffled sound of the passing train.
Anecdote
Malpas means 'bad passage' in Occitan dialect. It is believed that this name came from a questionable cabaret!
Le Malpas © Caroline Brandt
The strategic location of this passage could explain why there is a protohistoric oppidum at the top of Ensérune mountain.
The ruins of this village date back over 2,500 years. It was most likely inhabited by Celtiberians known as the Elisyces who were a tribe that occupied the whole region of Narbonne.
From the top, there is a beautiful view of the rolling hills across the entire region, the city of Béziers, the Caroux mountains, the top of the Canigo mountain and the star which represents the dried up Montady lake.
On the top of the tunnel, La Domitienne tourist office will welcome you and provide any information you may need about the region.
About 1 km further on, towards Béziers, is the village of Colombiers, river port, shops and restaurants!
A site managed by Voies navigables de France in collaboration with members of the “Entente du Canal du Midi” and their tourist operators.
