Tunnel of La Bête Refaite

The Tunnel of La Bête Refaite is a shipping tunnel on the first section of the Charleroi-Brussels Canal near Godarville, a village in the municipality of Chapelle-lez-Herlaimont, Belgium. The tunnel has a length of 1267 meters.
For the construction of the Charleroi-Brussels canal, 30 locks were constructed between Ronquières and Seneffe to bridge the enormous difference in height. The ridge between Seneffe and Godarville was an additional height of 15 meters to be overcome over a distance of 3 kilometers. This would have required 14 additional locks. In addition, a lock is constantly losing water to the downstream section of the canal, and there was a water shortage on the relevant ridge of the Hainaut plateau. The only solution was to construct a shipping tunnel.

Wikipedia