Planning a trip to Spain in Septermber 2018 and am looking for suggestions for the most interesting route to drive from Santiago de Compostela to Bilbao. We have 6 days.
Thanks!

Some places of interest maybe Lugo, Picos de Europa, and Santander/Altamira. I would also go past Bilbao to San Sebastian/Donostia. Also if go you in the opposite direction from Santiago,you can go to the spectacular Costa do Morte.

You will note that there are different languages as you cross the north. In and around Santiago, they speak Gallego, which is founded more in Portuguese than Spanish. And in the northeast they speak Basque which is of uncertain origin. That is why you will see variations in spelling now, and differences in accents and pronunciations once there.

......and what are your interests? There are two main routes from which you can take various side routes. There are too many for someone here to give you some decent ideas without you giving a great deal more of input. Something must have given you an idea to make this trip, what was that?
BTW all over Spain you will find ancient buildings going back to prehistory cave dwellings, art, good food and wine. beaches, mountains, clean air, walks.

These five days are the end of a three week trip through Spain. I'm thinking the northern route. Just looking for a route with more natural beauty as opposed to cathedrals and monuments.

Still a bit difucult to suggest but have a look at this.
Santiago de Compostela,
Lugo,
Taramundi,
Barcena del Monasterio,
Oviedo
Tanes
Covadonga
Póo de Cabrales
San Vicente de la Barquera,
Bustablado
Valle de Villaverde,
Bilbao.
Very much a cross country route with loads of scenery and mountainous roads.
Not all of these locations are going to suit you.However, I have given them so that you can see the roads I am suggesting may suit you and help to explore what you want to see. Of coarse you could simply take the A8 and miss a whole lot
I hope this helps. If you have any more questions please come back.

I traveled through this area last summer. You might get some ideas from my trip report.

Our itinerary from Santiago was: Lugo (we actually did that on the way to Santiago), Ribadeo (and the Cathedral Beach), Cudillero, Oviedo, Ribadesella, Potes (in the Picos de Europa), Santillana del Mar, Santander, Bilbao

Trip report - Criss-crossing the Camino: 5 weeks in Northern Spain (and a bit of France)

Photos (and blog report) Zenfolio | Isabel's_View | Galicia, Asturias, Cantabria

I agree that you might look at options that include a bit of the Picos de Europa, perhaps Potes.

You might be able to specify a "scenic" route when using viamichelin.com

For my trip report (which did not include Galicia):
Four Awesome Weeks in the North of Spain and Catalunya

Enjoy!

Thanks! So many good suggestions

As noted, first head to Lugo and then to Ponferrada and León before heading up to the coast on the AP66 to Lastres, before following the coast to Santander, past the Picos. You could start your coastal drive at Ribadeo, but that would mean you would miss Ponferrada and León unless you headed to Ribadeo from León through Cangas del Narcea and Taramundi, beautyful country. You will want to stop in Santander before driving to Bilbao.

https://iberiantraveler.wordpress.co...nd-the-camino/
http://www.iberiantraveler.com/Travels-in-El-Bierzo.pdf