The trail is a lollipop and the loop circles literally amongst the cement trenches of the Linea Cadorna (Cadorna Line) on the crown of the 614 m (2,015 ft) Monte Sasso. From the gun emplacements in the defensive line, you've got a commanding view into the Italian speaking Ticino province of Switzerland. The Linea Cadorna extended along the entire frontier of the Ticino (from Domodossola in the west to Chiavenna in the east). Of course the Swiss have always been neutral, so the defenses were never used and the trenches are in good condition for being 100 years old.
The loop around the crown varies from singletrack to forest road. The descent from the loop begins as a forest road and eventually becomes paved as it heads towards via Cardono and the city of San Fermo di Battaglia. The trails in this area are not well marked and maps are hard to come by, so you'll definitely want a GPX or the Trail Run Project mobile app
for this one.
Be sure to make the short detour to the overlook on the Pin Umbrela for a magnificent view of Lago di Como (lake) and surrounding mountains.