From Rifugio Gastaldi, take trail 222 heading south, descending about a hundred meters before climbing back up toward Colle di Arnas, a historic pass into France.

Leaving the junction for Colle di Arnas on your right, continue south through a landscape of small tarns and moraine flows. A steep and unstable section leads up to the Passo Collarin d’Arnas (2,847 m). From here, the view is magnificent, spanning the entire mountain chain that forms the watershed with France; notably visible from north to south are the Uja Bessanese, Punta d’Arnas, and Croce Rossa.

From the pass, descend rapidly toward the reservoir of Lago della Rossa (2,701 m). Nearby stands the Bivacco San Camillo, a useful shelter in case of bad weather. For decades, Lago della Rossa was the highest artificial reservoir in Europe, built upon a pre-existing natural lake. It is a popular destination for hikers, reachable via an easy trail from Val di Viù, and is famous for the spectacle of the spring thaw when blocks of ice float upon its waters.

Cross the lake by walking along the dam, then circumnavigate the eastern arm of the lake heading south. The route now continues with a steep climb toward Colle di Altare (2,903 m), with the characteristic Cresta dei Cugni on your left. Once you reach the pass, a short descent leads directly to the beautiful basin where Rifugio Luigi Cibrario (2,616 m) is located.