Inter-valley 105 begins from Aosta, from the district of Roppoz Porossan (722 m) and climbs up to the Viou pass, with an altitude change of approximately 2,000 m which highlights the changes in the natural environment as the altitude changes. It then proceeds towards the bivouac of La Liée, from where, having crossed the pass of Saint-Barthélemy and the Leché pass, a panoramic descent commences, which arrives in Lignan, a charming district within the municipality of Nus and the headquarters of the Regional Astronomy Observatory, the only structure of its kind, in terms of characteristics and instrumentation.

Having crossed through typical villages of the mid mountains, amidst meadows and larch forests, the itinerary ascends to the Fenêtre pass and reaches the beautiful grasslands of Torgnon, the splendid balcony over the Matterhorn, from where you then descend to Antey-Saint-André. The trail then goes back up to the 2,700 m of Mount Zerbion - the highest altitude of the entire itinerary and the 360° view over the mountains of Aosta Valley, as well as over the trail of the mythical “Mezzalama Trophy” (ski mountaineering).

The following stage proceeds on the crest as far as Portola pass and then descends as far as Champoluc, in the presence of the massif of Monte Rosa. From the wild Mascognaz gorge, the trail crosses the Palasinaz pass and then re-descends towards the Arp mountain retreat, passing by the shores of some magnificent lakes. From the Valnera pass, the descent begins towards Gressoney-Saint-Jean, a typical Walser village. From here the itinerary goes back up towards the final destination, Colle Valdobbia, on the border with the Piedmont region.