The Canal des 2 Mers cycle route follows the actual Canals de Garonne and the Canal du Midi and stretches 800km from the Atlantic Coast East of Bordeaux to the Mediterannean near Sete. Perhaps needless to say, as the route is along canals, it is flat, often shaded by large trees and very easy cycling. In fact, many of the people on the ubiquitous hire barges periodically unload their bikes and ride a couple of km before rejoining their slowly chugging barge/boat and beginning their next repass.
Starting at the Atlantic shore and heading East, you have the pleasant and gentle hills of the famous wine region of Bordeaux with many brilliant cycles out from Bordeaux itself. The Roger Lapebie trail is a must do especially if you combine it with a detour to the village of Saint Emillion. Continuing East, major towns of Agen, Montauban and Toulouse are great to explore before you get the the jaw dropping skyline of Carcassonne – definately worth a few days to explore.
After Cascassonne, the canal passes over the Tunnel de Malpas .This is where a road goes over a canal which goes over a rail line which goes over an old drainage tunnel…. Well, I find it interesting ! Take a short detour North off the canal to look at the Oppidium D’Ensurune. Return back to the canal to continue along to Beziers with the amazing hill of locks and then either head South to Narbonne or keep going East to Agde, Sete and Montpellier. Both Narbonne and Montpellier are on the TGV and RER rail lines so you can connect to airports from either.