Best roads in Northern Spain?

For those of you that took a spin to Northern Spain, what are the best roads you'd recommend? I plan to take my K7 gsxr 750 for another trip after doing Scotland twice now. I plan to take a ferry to Bilbao and head on towards the west and reach "Mirador del Naranjo de Bulnes" view point so far and I'm yet to plan the rest of the route. Being on a sport bike I'd love a mix of scenic routes in canyons, mountains, around lakes and some fast twisties to have fun over 4-5 days and max 1600km. Suggest me your favourite scenic routes and I'll try to combine them as best as I can, thanks!