The Greina Plateau lies between the cantons of Graubünden and Ticino. Even as early as the Roman era, important routes across the Alps led through this region. The plateau has remained an untouched jewel because it is still only reached on foot.
If brooks and rivers run only sluggishly above ground, hydropower is nearly impossible to harness. That is why the inhabitants of the valley of Le Locle began to use subterranean streams. This is how the cave mills of "Col-des-Roches" arose.