Help with trip to North Spain

Both places are already on the coast, so where along the coast to you want to visit?

We have a trip to that area late April - Bilbao and San Sebastian, then on to Segovia, Toledo, Madrid. Our understanding - and what we are seeing - is that public transportation in the area is quite good. We plan to take bus/train to Guernica, probably from Bilbao, and perhaps also travel to Saint Jean le Luz while in San Sebastian. There are several beaches you can get to via Metro from Bilbao, Google and Rome2Rio are your friends there...I am sure folks will jump in with specific suggestions.

Not sure about San Sebastian being "too packed" - do you mean crowded? Were you looking at something specific?

Thank you for the quick reply! Thinking about the National Park of Picos de Europa and that coast area (i.e. the town of San Vicente), it seems complicated using public transport.

Thank you Rebecca for the tips!, apologies for my language since English is not my native language.

I mean packed in time. visiting 3 cities in 4 days seems too much for me. That's why I will probably focus on Bilbao and Santander (Where I have the flights to and from).

In the future, please use a town’s full name. There are a number of San Vicentes in Spain. I assume you’re referring to San Vicente de la Barquera on the coast. There should be bus service to it. I can’t speak to getting to Picos de Europa park using public transportation, but I’m sure somebody will have an answer.

check Rome2Rio for transportation options. While not always accurate with schedules and prices, it at least gives you an idea of how to get to a place.

Thank you all, Jaime, yes it was San Vicente de la Barquera, apologies.
Rebecca I will double check my options, thank you again!

I can tell you that the Picos de Europa area was very difficult without a car as of 2016. In high summer (meaning not before the first week of July) there was a once-a-week one-day bus tour operating from Santander. I found it worthwhile, though I'd have liked a bit more time in the lovely (though touristy) small town of Potes. If that tour still runs, you can probably find it online. The Picos area is beautiful, but regular public-bus service was very, very limited at the time of my trip.

Santander has a very pretty beach, but the town suffered an extremely bad fire in the 1940s and doesn't have a great deal of historic architecture to admire. Both Bilbao and San Sebastian are more attractive in that regard. Santander wouldn't be my choice for 3 nights unless I had specific side trips planned that were more easily accomplished from there than from Bilbao, which I found a much more interesting city.

Not far from Santander to the west is the very popular Santillana del Mar, which retains its medieval architecture but gets a lot of tourists in peak periods--and it's tiny, so those tourists have an impact on the experience. Beyond Santander is Comillas, which has a few modernista buildings; I'm nuts for those.

Many thanks to all, I looked at Santillana and it looks lovely, I think I will spend a night there.
Acraven your information was super helpful! much appreciated.

Visiting Santillana del Mar is like walking back in time architecturally. As acraven said, depending on time of year if is extremely busy with tourists during the day, but great when they all leave by late afternoon. The last time we were there we stayed at one of the Paradors right in the historic center.

Comillas is quite interesting, as you can visit there El Capricho, one of the first works of Antoni Gaudi, the famous architect. Bilbao over Santander, and of course you can´t miss Donostia-San Sebastián.

We visited Castro Urdiales, and wished we had booked time to stayed there. A smaller city with a lot to see for it size.

Thank you all for the answers! Any recommendations or previous experiences regarding restaurants? I would love to try good local food. Many thanks, this is super helpful.

The actual Altamira caves are totally closed to public access and the only thing you can visit is a (bad) replica (IMO), and a museum of prehistory. If you want to visit caves, El Castillo and Las Monedas are open to the public, for example.