If you go back to Thonon and again turn south into D902, you will be traveling through the gorges of the Dranse, a large wild torrent that brings its waters to Lake Leman; the road passes through the heart of the Chablais, turning and twisting through small attractive cheese and ski communities until, after passing Les Gets, one arrives in the Faucigny region and the little town of Taninges.
It is a must, for your enjoyment of the natural beauty to drive on to Samoëns and Sixt, where you will reach what many people feel is the end of the world. At the end of the Giffre valley, a long mile beyond Sixt, you will come to a series of steep gray walls out of which multiple cascades fall from thousands of feet to form a famous sight called le Cirque du Fer à Cheval. These mountains look so very vertical because they did not fold; they could not—they could only jut upward, squeezed as they were between the Mont Blanc—Aiguilles Rouges group and the blocking nappes of the Chablais. They stand there like a fortress, best seen in the fall, when the crowds have gone home, golden light filters through the foliage, and the only noise is that of rushing water. The sight is so impressive that one can feel the presence of the creative force, and, personally, I always ache when I have to come down.