Underground mills at Col-des-Roches.
The over 400 years old mills of Col-des-Roches lie beneath the surface.
Carved out by the waters of the Locle Valley, the cave of Col-des-Roches underwent a remarkable conversion in the mid-17th century. Admire the engineering skills, which tamed an underground waterfall here and created hydraulic wheels that were used to drive mills, threshing machines and saws. The walk-in cave and adjoining museum tell this interesting story.