The A136 heading south from the France/Spain border near El Formigal, then left onto the N260 through Gavín - utterly fantastic. A better combination of bends, road surface & lack of traffic I have never found. Just don't venture onto the HU-361 at Sarvisé unless you like off-roading, although the view from the hotel in Nerin is worth it ([URL]http://www.ordesa.net/hotel-palazio/inicio.htm[/URL]).