A combination of digging and other work between the 15th and 18th centuries created a network of tunnels that were intended to support fortifications on the Rocher du Bock (the large sandstone rock that this road crosses), directly underneath the original castle in the area that was built in 963 by Count Siegfried. The Burgundians, Spanish French, Austrians and Germans all had a hand in constructing the Casemates.
