The N-621 through the Cantabrian mountain spine from the Hermida gorge to Fuente Dé — Spain's answer to the Dolomites, visited by a fraction of the crowd. The Potes valley, the Liébana monastery, and the cable car base at Fuente Dé closing 1,000 m beneath the high peaks.
Clone it to your planner, customize dates and stops, then ride. All free.