You start at the foot of Mt Blanc and then work your way over 2 passes to Switzerland. Great scenery, great road--- but just try to avoid during peak tourist hours. Plenty of straits to sort out the camper vans as they appear on the horizon.
This road winds through a spectacular gorge, some fast sweepy sections and a great set of hairpins. watch out for the 'tunnel du tende, a long, dark, narrow and bumpy tunnel with artics coming down the middle of the road at you. Apart from that, a blinder of a road and a great way to get to the Med, or even better, turn off at Breil and take the D2204 to Sospel and Nice.
The very famous Grimselpass, a stunning combination of breathtaking mountain drop-offs and wonderful super tight corners. This road tops out at over 2000 metres and so can experience some snow. Simply terrific, highly recommended, even though it is very popular with other bikers.