From the church square of Gromo S. Marino village (750 m) turn left and follow a paved road for about 2 km, then turn right when you see marked on a stone: 261 BAITE DEL CARDETO/233 PASSO PORTULA" (Cardeto Huts/ Portula Pass). A dirt road starts at this point (about 850 m). The transit on it is allowed only to authorized motor vehicles (bar on the road).
Il Club Alpino Italiano (C.A.I.) [...] ha per iscopo l'alpinismo in ogni sua manifestazione, la conoscenza e lo studio delle montagne, specialmente di quelle italiane, e la difesa del loro ambiente naturale.Statuto del Club Alpino Italiano, Articolo 1
From Rifugio Fratelli Longo (2026 m), the path leads directly to the bottom of Mount Sasso valley. Go downhill near the creek to about height 1800 m. The path now turns left (eastward) and enters the Brembo River Valley. Going along the hillside in a sparse forest and heading upstream in the valley, you reach quickly Rifugio Armentarga (private Hut 1776 m).
The path begins slightly above Grabiasca hut (1443 m), reached from Grabiasca Village (750 m) by 255 path. Beyond the hut, climb up to height 1550 m; here leave the path 255 turning left (westward) and cross Grabiasca Valley staying along the hillside with small height changes. You could have some difficulties in crossing, after rains or thunderstorms, a gorge with a creek in it.
Starting points: i) from the small church of Ripa Bassa di Gromo (859 m) free parking area; ii) from Gromo village north skirts (around 700m). Form Ripa Bassa heading to north, the path follows partially a forest road and a mule track, crosses an area with huts and meadows up to around 1200 m. Here you enter a dense forest.