Follow the trail that descends from the Rifugio Gastaldi toward the outlet of the Crot del Ciaussine basin, heading in the direction of a small waterfall formed by the stream flowing down from the basin below Cresta del Fort.

After crossing the stream, the trail climbs along the grassy, debris-strewn slope between the waterfall and the slopes of Rocca Affinau. After a short climb, you reach the junction for the Colle d’Arnas; the Tour route ignores this turn and follows the left-hand path, which skirts around Rocca Affinau while staying in the valley on its left side.

With a series of steep switchbacks, the trail leads to a basin where you encounter several meltwater ponds. Once you reach the steep debris slopes that close off the basin, a short, well-marked trail climbs them on a leftward diagonal, leading directly to the Collarin d’Arnas (2,850 m).

The trail descends over glacially smoothed rock slabs toward Lago della Rossa and its dam. Shortly before the dam, on the left side of the trail, you come across the Bivacco San Camillo. After crossing the dam, follow the dirt road that skirts the lake, then turn left. Ford a small stream and continue along the left (hydrographic) side, heading toward the bottom of the basin.

Climb a ramp that begins near a small waterfall and, via an easy route, leads to the Colle Altare (2,962 m). From the pass, follow the track that leads into a wide gully, keeping to the right-hand side and alternating gentle traverses with steeper slopes, descend to a flat area dotted with small pools and bordered by Lago di Peraciaval. The well-marked trail crosses the plateau and leads to the edge of the drop overlooking the Piano del Sabiunin, from where a few steep switchbacks bring you up to the Rifugio Cibrario.