Blisworth Tunnel has no tow path inside, but is wide enough for two narrowboats to pass in opposite directions. Work began in 1793, but errors by contractor left a wiggle in the tunnel, and after three years work it collapsed due to quicksand, claiming the lives of 14 men. It was then decided to begin again with a new tunnel. By the time the rest of the Grand Junction Canal had opened between London and Braunston, Northamptonshire in 1800, apart from the crossing of the River Great Ouse, the section of canal from Blisworth to the lower end of Stoke Bruerne locks
Riqueval Tunnel Riqueval Tunnel The Riqueval Tunnel is a -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