Canal de l'Aisne à la Marne, Summit level canal in northeastern France

The Canal de l'Aisne à la Marne runs 58.1 km from Berry-au-Bac to Condé-sur-Marne, with 24 locks (16 on the Aisne side, 8 on the Marne side). Its 11.9 km summit level crosses the Mont de Billy through a 2,302 m one-way tunnel. The lock walls are dark, mottled stone, and the canal is edged with vertical wooden piling.

Construction began in 1841 and the canal opened in 1866 as a link in a broader network designed to connect the Loire with northern France. The project demonstrated France's commitment to modernizing its transport infrastructure during the industrial age.

The canal's name comes from the two rivers it links, the Aisne and the Marne. Grain is its main cargo, carried by about ten péniches a day, while pleasure craft are mostly private boats in transit. In Reims, 18 km of towpath form the Coulée verte, a cycle and walking route with benches, fountains and information posts.

The canal banks are easily accessible for walking and observing lock operations throughout their course. The best visiting season is spring through fall when more boat traffic is visible and the towpaths are most pleasant to walk.

The Mont-de-Billy tunnel is 2,302 m long and carries the canal under the watershed on a single-lane, alternating one-way passage. During the First World War it sheltered artillery pieces mounted on boats. The canal's summit level lies at 99.59 m, fed by intakes from the Vesle and by pumping from the Marne at Condé-sur-Marne.