From the Coda mountain hut, the route goes around Punta Sella on the right to Col Sella, where the fairly steep descent begins down towards Goudin Lake.
After going along the lakeshore, the path winds its way down through the vegetation to the Serrafredda pasture.
At the fork in the middle of the pastureland, continue on the right, up over a wooded ridge that leads to the Goillas pasture.
Cross the Goillas torrent and go downwards along the dirt-track road for about 500 metres until you come to the Leretta pasture, then begin walking up the path through the fields above the trail: from here, a long up and down path begins that leads through conifer woods and clearings of pastureland to the Crêt Damon and Lion pastures.
From the latter, the route takes left in the pastureland and leads into a steep stretch of woodland that goes down towards Lake Vargno.
Go past the mouth of the lake, down from a dam, and after a brief stretch, go up again on the right along a convenient mule-track, along which the procession runs to the Oropa Sanctuary and which is the main access route for the Mont Mars Nature Reserve.
The itinerary continues without difficulty through a very varied environment, touching upon pastureland, stony ground and roches montonnées, on towards Lac Long and after a rocky rise to the basin of the Barma Lakes (Lacs de Barme).
From here, walk towards the largest of the lakes, ignoring the fork on the left that indicates the continuation of the Alta Via, and you will soon reach the Barma mountain hut.