Maybe a tad too short for what you're looking for, but surely can be complemented with side-trips to visit nice locations, and judging by the places it goes through, you will have beautiful countryside, and seaside too !
It's called Pirinexus, and joins north of Catalonia in Spain with Southern France, I think there are still some sections undergoing proper signaling etc, but several people already reported that could successfully ride it.
http://www.pirinexus.cat/