This route has 'epic' written all over it, twisties all the way up of nearly every variety, possibly better going north to south, but great either way. You'll get the most out of it on a clear sunny day. There's nothing more to be said really, except go ride it!
I think this is the highest mountain pass in the area, just over 1,900m and it gets quite cold at top, nice views when its not misty.
The road surface is good & wide, and as you can imagine with a mountain pass lots of corners. Was quite wet when i went along here in late May 08 but still worth it for scenery.
Places of interest on the way is (not sure of name, in English is something like Valley of the Dead) Church where Franco is burried (bit of a controversial place, in Spain, as Franco built it using soldiers captured during the civil war, a lot of whom died making the place) then onto El Escorial, burrial place of all Spanish royalty, impressive building.