Last part of the climb from Yesa, also known as Belagua has amazing scenery, watch for ponies on lower slopes, goats and for when the road turns right over itself near the top!
Spectacular scenery and lovely corners but the surface on some parts are not the best. Also look out for the clouds/fog which can come in very quickly which can reduce visibility to a few feet, not what you need when you have one hell of a drop on one side and hard rock on the other!
Much of this is very tight with virtually mo run-off and frost damaged surface. The views however are truly spectacular and on a clear day won't fail to impress. The combination of forests and geological features make for a great contrast, road surface starts off badly, but improves a lot as you come down on the Spanish side.