Malvaglia for experts
At the beginning of the Blenio Valley there is a trolleybus from Malvaglia (with bike transport) to Degro. An official Switzerland Mobile tour, the Valle Malvaglia Bike, starts from there.
You can also avoid taking the trolleybus and ride from Malvaglia on the small asphalt road that will take you directly to the ascent of the loop.
The trail is up and down high above the valley, fun and with nice views.
Back in Degro, however, begins the super tough descent back to Malvaglia, recommended only for those with good riding technique. It is a rocky trail that gets more and more technical as you descend. Slow, with lots of tight turns, and very hot in summer. You will sweat seven shirts to stay in the saddle.
The final part is on steps carved into the rock, not trivial.
The alternative, not very glorious, is to go down the paved road from Degro.