Below is a map of my favourite big climbs by mountain bike in the Alps. (OK, there are a couple of rides from the Juras and (scroll down), the Pyrenées).
A few pics first:
Cycling to 3000 metres:
There are endless huge climbs up high on little farm tracks, or old miltary roads, or ski-lift service tracks, or etc. Usually I find these routes just by staring at maps.
Often these are the greatest days out, as there will be ZERO traffic, and just the great outdoors.
To skip the map, see here for a fairly complete list of blog posts.
Feel free to suggest any other ideas that you may have ridden.
I know the map looks a little messy with the Col names. BUT I think you’ll appreciate the labels as you zoom in. Click on the icons for links to blog posts of the ride.