The descent on the Swiss side is easy enough, but it's rather long. The last part is along a road, but at least you'll make short work of it. From Trient, it's time to join the UTMB course, with the climb towards Les Tseppes, and then Catogne. Most runners do this bit at nighttime, which is a shame considering how beautiful the view is. The trail is typical UTMB: easy enough, after a series of tough switchbacks to start with.

At Catogne, keep climbing towards the small col to the south, where a short descent will bring you to Col des Posettes. There, you'll have the option to directly descend to Le Tour or make the short climb to Aiguille des Posettes. As it's only 200m of ascent, and you'll be treated to a stunning panoramic view on a trail that initially follows the ridgeline before turning into a fun singletrack snaking around the trees, I suggest choosing that option. This section is a part of the Mont-Blanc Marathon course, and will keep you away from the mountain bikers as well. The trail will bring you right back to the car park where you started.