“A hard climb up to the Pian delle Betulle for those that don't want to take the lift.
— Lost Justpastnowhere
Part of this road is open to vehicular traffic, but the route is mostly gravel and cobblestone with occasional cemented sections. This is not a technical trail, but it is quite the climb, averaging 11% grade. And to be particularly wicked, the steepest parts are near the top, so it gets you after you're already tired.
This route starts in Crandola Valsassina, where there is one of many monuments and memorials to the partisans that were active in this area during World War II. From there, a number of switchbacks make the climb somewhat more palatable. Around 5 km (3.1 mi), you'll reach the tiny hamlet of Alpe Grasso after a particularly steep climb, and then it's one more steeper grunt to Pian delle Betulle which is a flat, open area below the summit of Cima del Laghetto (1,733 m; 5,700 ft).
If you are doing the Brigata Rosselli loop, you can skip this climb by taking the diversion to the Pian delle Betulle lift. And of course you can descend this road too, but there aren't any technical features to keep you occupied.