The Canal du Midi end to end by towpath and regional train — Riquet's water supply in the Montagne Noire, the summit at Naurouze, the lock staircase at Béziers, and the oyster lagoon it empties into.
Toulouse
Start where the canal does. The Port de l'Embouchure, where three waterways meet, then the brick city above it — the Jacobins church, the Sunday market on the Prairie des Filtres. Toulouse is a working city of half a million people and prices it accordingly, which is to say cheaply.
Toulouse to Castelnaudary
The first towpath day and the easiest: flat, waymarked, and shaded wherever the plane trees are still standing. Castelnaudary is the cassoulet town and its port is the widest basin on the canal, dug so barges could turn.
Naurouze and Saint-Ferréol
Out to the watershed at the Seuil de Naurouze, 189 m up, where water divides between the Atlantic and the Mediterranean and where the canal is fed. Then up into the Montagne Noire to Saint-Ferréol, the reservoir Riquet dammed between 1667 and 1672 to prove the summit could be supplied at all.
Castelnaudary to Carcassonne
Down the flight of locks at Saint-Roch and east along the Lauragais. The towpath surface gets rougher through here — this is the section that punishes narrow tyres — and the villages thin out, so carry lunch.
Carcassonne and Lastours
The Cité early or late; between eleven and five it belongs to coaches. Viollet-le-Duc's nineteenth-century restoration invented the pointed slate roofs, which are wrong for the region and are now the thing everyone photographs. Lastours in the afternoon: four Cathar castles on one ridge, and nobody there.
Carcassonne to Le Somail
The longest day on the bike and the best one. Past Trèbes, through Marseillette and the Minervois vineyards to Le Somail, a canal hamlet that is essentially one bridge, one chapel, one ice house and a second-hand bookshop with fifty thousand volumes in it.
Down the Robine to Narbonne
Leave the main line at the Cesse lock and follow the Canal de Jonction south, down the seven Sallèles locks to the Aude. There is no aqueduct here: the route crosses the river itself, 800 metres of open water between the Gailhousty and Moussoulens locks, held deep enough by a fifteenth-century weir. Then the Canal de la Robine into the middle of Narbonne, where it runs under the Pont des Marchands with shops built on top of it.
Fontfroide and the lagoons
The Cistercian abbey at Fontfroide, in a dry fold of the Corbières with a cypress alley and a garden that survives on very little water. Then the Étang de Bages-Sigean, a lagoon of flamingos and salt, and Gruissan if the wind is not up.
Béziers, Fonseranes and Ensérune
Train up to Béziers for the lock staircase at Fonseranes, eight oval chambers cut to raise boats 21.5 metres in one flight and the busiest thing on the canal — though the bottom of the flight has stood idle since 1858, when the aqueduct over the Orb opened and boats stopped needing to reach the river. Then west to the Malpas tunnel — dug in 1679, the first tunnel ever built for a canal — and up the hill above it to look down on the Étang de Montady, a lake drained in 1247 by radial ditches that still radiate.
Béziers to Agde
Over the Orb on the aqueduct that replaced the old river crossing in 1858, then east through Villeneuve and Vias to Agde. The round lock at Agde is circular because three waterways meet in it at different levels, and boats turn inside it rather than reversing.
Along the Thau to Sète
The last lock at Bagnas, a single chamber and the final one before the sea, then out onto the Étang de Thau with the oyster tables standing in rows offshore. Stop at Bouzigues and eat them at a table on the water, which costs about a third of what the same shellfish costs in Paris.
Sète, and out
Up Mont Saint-Clair for the whole route laid out behind you — lagoon, canal, and the Cévennes on a clear day. The marine cemetery below it, water jousting in the canals in summer, and then the train to Montpellier, half an hour away, for onward connections.
Good to know
The towpath is the Canal des 2 Mers à vélo and it is not uniformly surfaced: roughly half of the Toulouse–Sète run is stabilised or asphalted and the rest is packed earth that turns to clay after rain. Use something with 35 mm tyres or wider; a road bike will be miserable between Castelnaudary and Trèbes. Voies navigables de France closes towpath sections for tree felling, almost always between October and March — check their notices before fixing accommodation, because a closed section means a detour onto a D-road. Bikes travel free on Occitanie TER trains and cannot be reserved, so avoid the 7am and 5pm services. One-way bike hire between Toulouse and Sète exists but carries a drop-off fee worth asking about before you book. The real hazard is July and August heat on the stretches where the plane trees have already gone: there is no shade, no drinking water from the canal, and the middle of the day is genuinely dangerous. Ride early. If you are hiring a boat instead, note that the locks work roughly March to early November and the canal closes for maintenance in winter.
Shorter or longer?
Turn west at Toulouse instead and ride the Canal de la Garonne to Bordeaux — about 250 km, fully surfaced, and five or six days. The two canals together are the Canal des 2 Mers, sea to sea.
Six days from Carcassonne, using the train for the long hops and the bike for day rides from Narbonne, Béziers and Agde. You lose the summit and the reservoir, which are the engineering half of the story.