Has anyone been to Picos de Europa National Park in northern Spain? I’m planning a trip next year starting in Madrid then heading north to the coast (Santander, Bilbao, San Sebastián) before crossing into southern France (Biarritz & Toulouse) then east to the coast and working down to Barcelona. Wondering if we should go into Picos de Europa National Park for some hiking? And if so should we stay in the park a few days or just do a day trip from Santander? Then if we do stay in the park where should we stay and what hikes are suggested? Not looking to do all day hikes, maybe just 3 - 4 hours, relatively easy hiking.

I've spent several vacations in the Picos de Europa, both on the Asturian side and the Cantabrian side. I would definitely not do a day trip from Santander, as you wouldn't do justice to the beauty of this area----it's really stunning every where you look, and one of my favorites places in Northern Spain.

I've based on the Asturian side outside of the "capital", Cangas de Onís, and on the Cantabrian side (much closer to Santander) in or near the mountain village of Potes. The Hotel del Oso is an absolutely charming place to stay and to dine (with 2 adorable St. Bernards) in Camaleño. There they can advise you regarding easy hikes, as they're the experts.
Hotel del Oso

Either Cangas, Asturias, or Potes, Cantabria make a good base, but if coming from Santander, Potes & environs is your best bet, as it's closer, from the coast at Unquera down the sinuous Desfiladero de la Hermida.
There is a nice circular hike just south of Potes starting in the village of Mongrovejo that's easy (as in moderate).

https://www.alltrails.com/trail/spai...-tanarrio-redo

If you chose the Cantabrian side, you can also hike down from where the funicular alights,, the Mirador del Cable, atop the mountain above Fuente Dé, but it may take more than 4 hours. I haven't done the descent yet from the top of the funicular down to Espinama. This is the alternative to taking the cable car back down to Fuente Dé.
https://www.wikiloc.com/hiking-trail...inama-38718220