Great Trench of the Nantes to Brest Canal

At an altitude of 184 m, the Glomel trench is the highest point of the Nantes-Brest canal and the watershed between the Blavet and Aulne basins. The canal project and its passage through the center of Brittany dates back to Vauban, the decision and the route to Napoleon. The impressive trench allows the Aulne and Blavet watersheds to communicate via the canal.
The Grande Trenche of the Canal from Nantes to Brest was dug in the 19th century by deserters from the army of Louis XVIII. The 4000 convicts of Glomel had to move as much earth and rock as was necessary for the construction of a great pyramid in Egypt. It took 9 years to create this trench, more than 3 kilometers long, 100 meters wide and 23 meters deep.

To cut the canal through this mountain, the highest point along the chosen route to connect Nantes with Brest, was one of the most labor consuming, pharaonic tasks for the crew, involving thousands of forced and prisoner labor in addition to the hired workers. By the time it was finished, Napoleon's original plan to resist a British blockade via inland canals had long been passed, and the canal never lived up to any projected economic transport benefits.

Here the canal meanders through the landscape.