The best way to appreciate the features of this valley is to follow the Nature Trail by foot (approximately 3 hours to and back) which starts from the Rossiglione sports field that you can reach by following the SP 1 in a northerly direction, at the 2-kilometre point. From this point you can see how the Torrente Gargassa deeply carved the brown-coloured sedimentary rock (conglomerates and breccias) accumulated here during the Oligocene epoch as part of the Tertiary Piedmont Basin (TPB).
From the lay-by you can see the different forms of the ridges in relation to the various types of rock contained therein. The conglomerate ridges are generally characterised by very steep walls created due to systems of sub-vertical fractures, while the serpentinised lherzolites steep slopes are formed with numerous outcrops and very little soil. The ridges formed by serpentine schists have relatively well-developed soil where mixed forests grow with rare rocky outcrops. The ridges made up of calcareous schists, on the other hand, can be identified by their hill-like form, gentle slopes, and dense mixed forests on considerable soil that rarely exposes the underlying rock.
If you check out the different types of vegetation you will see that they too reflect the geological substratum underneath. Conglomerates give life to specialized vegetation that grows on sun-baked slopes with no soil and
very little water, such as Euphorbiaceae and Cerastium utriense; on periodites – both serpentised and non – where small pockets of stony soil are created, we mainly find pine trees (partly favoured by human intervention). These soils are rich in magnesium and heavy minerals, but low in calcium and clayey minerals so vegetation really struggles to grow there. Plants such as Dafne cneorum, Cerastium utriense, and Cheilan-thes marantae, which were more widespread once upon a time, have adapted to living in these soils where there is less competition. Flourishing mixed woods grow on the ridges formed by softer rock such as serpentine schist and calcareous schist. The particular toponomy of this site called “Cava dell’Oro” is justified by small auriferous mineralisations, inside quartz veins, in the past exploited at local level for the extraction of the precious mineral.
Primary auriferous evidence is also present upstream of Rossiglione and this led to a widespread, though low, presence of metal in the torrents. For centuries this led to the activity of “fishing for gold”.Indeed in the 18th century and the early 19th century, some of the residents of Rossiglione were considered experts.