Riqueval Tunnel

The Riqueval Tunnel is a 5,670 metres (3.52 mi)-long tunnel on the St. Quentin Canal, close to the commune of Bellicourt, in the department of Aisne, France. It connects Bellicourt with Bony. It was constructed as part of the St Quentin Canal between 1801 and 1810, on the orders of Napoleon. The tunnel remains in use, and can be traversed using a chain boat. Along with the Mauvages tunnel, on the Marne–Rhine Canal, it is one of the last locations in the world where a system of chain towing is still in operation. It was the longest tunnel in the world until the construction of Biassa II tunnel, La Spezia, Italy.

Tunnel data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).