Summit section with summit tunnel in Pouilly-en-Auxois
The summit section on the Canal de Bourgogne is 6 km long. Due to the terrain, this length could only be achieved by using a tunnel. This is 3333 m long and completely straight, so that you can see the other end from one end. It is up to 34 m below the surface of the earth.
Source: Wikipedia
And we really didn't notice; in Pouilly-en-Auxois we crossed the main European watershed between the Atlantic and the Mediterranean.