Bilbao, Basque Country: 3-8 hours
If Bilbao isn’t already on your itinerary, it is a quick side trip from Northern Spain. You can make the architectural appreciation loop from bridge to bridge on either side of the river in about an hour. The Guggenheim collection can be appreciated in about an hour as well. That leaves time for pintxos on a plaza, aimless wandering and maybe even a trip to the beach. Here’s what I recommend as a base plan:
Breakfast, coffee or snack time: Panaderia Pasteleria Jardines is REQUIRED. These breads and pastries will leave you weak in the knees, so make sure you get a jolt of cafe con leche with your order. There is no website and it’s ot in the tourist books, but clearly ther’s a connection to Le Cordon Bleu. Address: Jardines, 10 Bilbao, 48005 Distrito: Ibaiondo - Barrio: Casco Viejo
Casco Viejo and Pinxtos: take spontaneous turns. There’s no way to get lost in this medieval neighborhood. Guys, stylish ready to wear menswear can be found here. At some point meander to Plaza Nueva for pinxtos and don’t be shy. Get as many as you need to feel satisfied. Really relax and dig in while in Blibao - and there’s free WiFi. Go right before siesta time - about 1pm - not many tourists at that time.
Walking Tour: From Casco Viejo, go to the Ria del Nervion, choose a side, and walk North along the river. Follow it as it turns to the west, to the Deustuko Zubia bridge. Cross and walk back down the other side. Along the way, you may decide to cross other bridges, people watch in plazas, visit the Guggenheim, have a drink, etc - great ideas on all fronts.
Art & Architecture: Bilbao has it. Even their city marketing program is cool (Bilbobus, Bilboats, etc). Of course you’re going to see the Guggenheim - at least walk by it. Personally, I was done with the collection in 30 minutes and moved a few blocks up to Museo de Bellas Artes de Bilbao. The art collection at Museo de Bellas Artes de Bilbao was much more fascinating to me because it lacked the international art star zing and educated me on Basque, Catalonian and Spanish artists.
The Beach: It’s only 20-30 minutes away, but it was raining when I was there so I did what is listed above plus some. Check out what Liz Pitt says about the 4 Gorgeous Beaches of Bilbao and add that to your list of possibilities. Best part is, you can take the Metro - here is some guidance for enjoying the beaches from the Bilbao Metro.