driving A coruna to Bilbao?

There are a lot of prehistoric caves in Asturias and Cantabria, together with the Basque Country (both sides) and Aquitaine is the area known as the Sixtine Chapel of cave art in the world. The whole northern Spain is rainy, mountainous, with beautiful valleys and a rough sea. Bilbao makes a great departing point to visit Vitoria-Gasteiz, Rioja, Donostia-San Sebastian, Santander...on our cheap, efficient, clean and timely public transport. Lots of hikes everywhere, you´ll love this area, much less visited than the usual visits of Spain.

I'm thinking if you drop Galicia you could tack on the region of Navarra and points east instead, including parts of the Pyrenees and those picturesque towns starting in Olite, heading east to Sos del Rey Catolico, down to Tarazona, then looping back to Laguardia, before ending in Vitoria-Gasteiz.

As for the Picos de Europa, I've hiked there a few times and really enjoyed it, mainly using the Parador hotel at Fuente Dé as a base to explore and hike. The next door teleferico zips you up to the higher elevations in no time.

I enjoyed a day trip to Vitoria-Gasteiz from Bilbao. Vitoria-Gasteiz has a nice, large historic district on a hill; escalators are helpfully provided. The stored-value card needed for public transportation in Bilbao also worked in Vitoria-Gasteiz as of 2016. I liked Bilbao a lot and was glad I was spending multiple nights there.

I found the old stone town of Potes in the Picos de Europa very atmospheric though not undiscovered.

Tarazona and Olite were fun because I felt like the only foreigner in town.

Laguardia is a charming old hill town in the wine country. There's at least one parking lot below the town with an elevator to take you where you want to go. Laguardia gets a good number of tourists.

Other places that might fit into a more condensed itinerary include Burgos (pretty historic center with lots of pilgrims), Santillana del Mar (medieval architecture swamped by visitors), Comillas (modernista architecture, including one building by Gaudi), Leon (historic district now full of lively restaurants and bars; one Gaudi building) and Astorga (one building by Gaudi).

Oviedo is a quiet city with some historic architecture, including exceptionally old churches. Gijon is noticeably livelier in feeling but has only a tiny historic area. There is some attractive late-19th century/early-20th century
architecture, though.

Santander suffered a dreadful fire in the 1940s, so it doesn't have a lot of old architecture. It's not unpleasant, but unless you want to look at the magnificent beaches, I think it's skippable.

I will agree that between central Asturias (let's say Oviedo) and central Galicia (let's say Lugo), it is perhaps a bit less interesting than between Oviedo and Santander/Bilbao. The coast is beautiful still, and the mountains are very rugged, but there are few "top sights". Cathedral Beach might be one, but I felt it was a bit overrated (it is no Étretat). Some of the fishing towns are cute, but there are plenty of those in Euskadi (Basque country) and Cantabria too.

So, yes, perhaps save Galicia for a later trip? It combines really well with a trip to northern Portugal, and there is much more to Galicia than churches.

I’ll just add to what Carlos mentioned. Earlier this year my wife and I spent 8 nights in Santo Domingo de la Calzada, Olite, and SOS Del Rey Católico, using them as bases for days trips. There is a nice walk at Foz de Lumbier. We could have used more time in that area and overall, there are very few tourists.

If you decide to drive along the north coast, stop at cathedral beach and you already know there is plenty of hiking in Picos de Europa. So many places to see and so little time.

Ribadasella would be a good stop. Cueva de Tito Bustillo is in town and is perhaps second only to Altamira for its paintings (make reservations for Tito Bustillo in advance). You can hike in the Lagos de Covadonga in an hour, and get transport for the Ruta del Cares from Covadonga. There are seasonal access restrictions on dring to Lagos de Covadonga, if driving yourself you need to be at the access gate by 8 AM, otherwise there is a bus.

If you want to concentrate on the hiking, Las Arenas de Cabrales is a good base. You can get to the Lagos from there (1 hr), and there is a bus (10 mins) from town to Poncebos, one of the termini for the Ruta del Cares and also a hike up to Bulnes. Unless you are acrophobic, you should not miss the Ruta del Cares. Apart from an initial (uphill stretch, it's level hiking along the side of a dep gorge

There are also quite a few caves in Cantabria. You can do both El Castilllo and Las Monedas in a single morning or afternoon, they are just a short walk apart.