Start : Prelles' bridge under the national road

The rock through which the tunnel has been cut is a quartzite, a metamorphic, siliceous rock which is very hard and formed by grains of quartz welded together. It originates from sand deposited 230 million years ago in the still-shallow waters of the nascent Alpine ocean, and brought here by the erosion of the surrounding topography. In places, undulations can be seen on the tunnel wall: these are ripple marks, "fossilised" creased created by water flowing over the sand. 

The mountains are areas naturally used for agriculture. These agricultural practices have been carefully thought-out in order to protect the environment. Agri-environmental measures have been introduced. They are designed to encourage and remunerate volunteer users of mountain spaces in their actions to protect natural environments. These measures prevent over-grazing, the invasion of bushes and shrubs and the proliferation of invasive plants. 

The symbol of the Southern Alps, this softwood tree loses its leaves in winter, and is swathed with gold and lights up the mountains in autumn. The larch forests are maintained by the grazing of flocks. Without them, other trees like the fir or other pine trees could grow, creating a different kind of forest. A pioneer species, the larch establishes freely in light conditions. Its solid rot-proof wood has always been used in the construction of houses.

On this path, you will pass by some eco-constructed cabins. One of them is made from larch, a wood that is naturally resistant to bad weather and insects and needs no previous treatment. The other is constructed according to the “post-beam” principle, which is reminiscent of half-timbered construction. This is characterised by an exposed supporting framework. The beams support the roof, and these beams are in turn are supported by the posts.