The three massifs of the of the Picos de Europe are bounded and divided by deep gorges. The best known and most dramatic is La Garganta ("throat") of the Río Cares.
The Río has its source in the Province of León to the south, more than 12 kilometers from the mouth of the gorge at Poncebos. (Near Arenas de Cabrales)

Link to map off this site: (Slow download) http://www.iespana.es/imagenlmrv/picosdeuropa/mapa.html

Every summer, thousands of visitors hike this trail. While not technically difficult, it requires being in reasonable physical shape and wearing comfortable and well-fitting footwear
We found it to be a very memorable experience, and well worth a few sore muscles and foot blisters at the end of the day.