Here's my short list of unknown places well worth visiting in Spain. For when you tire of the well-known destinations such as Barcelona, Granada, Sevilla, Toledo, Bilbao, Segovia, Santiago etc

1) Asturias and Cantabria. Okay, so they're not unknown in Spain, but many tourists don't know of the superb mountain and coastlines you can find here..

2) Leon, Zamora, Salamanca parts of Leon-Castilla. Full of historic towns, cities, castles and monasteries etc.

3) Cazorla national park, Andalucia

Another good topic, filbert. In my experience with other travelers to Spain (aside from Spaniards, that is) one of many often overlooked regions of Spain is Galicia. Some know about Santiago de Compostela but few. When I traveled throughout Galicia we did see lots of tourists but they appeared to all be SPANISH!

The same went for País Vasco/the Basque Country. In fact, most of Spain's norther region (west of the French border) seemed to be mainly untouched by non-Spanish tourist.

As you said, most non-Spanish tourists tend towards the larger, metropolitan regions of Spain because, well, clearly they only have a short time to visit Spain so they focus on these. Logical. I'd personally love to spend an entire month just traveling around Galicia and another month in País Vasco and another in Cantabria. OR, just take 3-months to cover as much of the north coast as possible.

Saludos, MadridMan

This is a great topic! Can I add a few? Caceres is an absolutely enchanting city--so well-preserved and beautiful. I was recently reading the section of Penlope Casas' Discovering Spain (I think that's the right title, it's the one where she goes all over Spain, suggesting hotels and restaurants as well as providing background) where she talks about Caceres and was inspired to pull out my 15 year old (gasp!) photos of it. In that same area (generally) I would include Trujillo (old castle ruins up on the hill and a lovely plaza mayor) and Merida (tremendous Roman ruins and a great museum). I never would have sought these places out on my own, but was traveling with two friends who rented a car and wanted to see those parts of Spain. I am so glad that I went with them!

Yep, I have been to caceres,merida and trujillo. The best thing about these places are the roman ruins(ampitheatres and such).They not necessarily known as the more beautiful places in spain. These places have a real small town feel. I remember eating a three course meal for 10 eur in one of those cities.One other point is that spaniards are protective of their regions and have stereotypes.I remember when i lived in sevile I mentioned to some spaniards that I wanted to go up north. They said be careful, they will kill you(ETA).

Sorry, other than passing thru and seeing many Oliveras I haven't visited Extremadura. But I do love Pontevedra and the Braga / Guimaraes area of northern Portugal across the rio Minho. I could spend months just exploring the Celtic ruins there in northern Portugal & Spain's Pontevedra.
BTW
A little known fact: On return from his first voyage of discovery, Columbus' landfall was in Baiona (at the mouth of the ria de Vigo). Then he followed the coastline down to Huelva.

And the Parador de Baiona (the Conde de Gondomar) is not to be missed. Wonderful.

I'd agree with MM on the Galicia point. I was there a couple of weeks ago staying with a friend. It really makes a change to see rolling green hills and forests. I stayed in Lugo which is small and cosy with the city wall intact all of the way round. It was a party atmoshpere compacted into a few streets in the evenings which made it possible to bar hop with incredible ease. If you like seafood then Galicia is the place to be. I ate some amazing stuff whilst there. I flew into and out of La Coruña which was also a nice change from Madrid. The flights were seriously cheap as it's a new route with www.spanair.es

Yes! Both Cazorla and Mérida are on our itinerary! Glad to see both make the grade here as places that are a bit out of the way, must sees, and "neglected" by American tourists. (Spanish tourists are fine - would love to meet a few!)

Also would love to get to see Galicia (especially after seeing "The Sea Inside"), but Spain is just so big and there is just so little time. I suppose there can always be "Spain Road Trip - Part Two"!

Having visited points one and two of filbert's list, can only second your recommendation.

Asturias is great, the mines and steel factories are mostly down (bad for the locals, good for tourists), you have the Sea, you have the mountains, and you have plenty of Spain's oldest architectural heritage at hand (pre-romanic churches, for instance). And except for the Pico de Europas area which is partly Asturian, but well visited from people of all places, you won't find a tourist.

I spent two weeks in Oviedo this April and May, and apart from mostly being the only guest in my small hotel, I have not seen any other foreign tourist in the entire city and not even in the Internet cafés. Asturias and the entire North is also very different from Central Spain or again from Andalucia as far as the people are concerned - the North is predominantly Celtic which is a very different kind of people to the Arab-influenced Andalusians, for instance.

León is doubtlessly a first class address when looking for historic monuments, as are Zamora or Salamanca. León was capital of the country for many years, and the richness and variety of remains shows it. The fresco's of the Royal Pantheon are a must - from Oviedo, I drove over to León just to see them again, that much I liked them during my first visit many years back. And they are very typical for Castilians and their menthality, much more than Madrid or Segovia are.

Cazorla, Baeza and Úbeda are still on my "to do" shopping list for a trip in the future.

Perhaps one completely forgotten region to be added to the list: I found the region of Soria very sympathetic too. Quite a few worthwhile monuments, rolling hills, and again - unlikely you'll meet any foreign tourist.

Spain, to the last poster, is not a country. It is a continent.

Top three "neglected" places:

3) Bermeo. Once the most important seaport on the northern coast, and a critical fishing fleet HQ, Bermeo is now a quaint fishing village on the Vizcayan coast...very close to Bilbao...and incredible Basque seafood available at a myriad of restaurants

2) Covadonga/Picos de Europa/Cangas de Onis, etc. Not really "neglected" since it's a religious pilgrimage site, but the non-die-hard travelers who come to Spain for the beaches, etc. have no idea this place even exists! It's in the middle of the Picos de Europa for the most part, and on the drive up, you'll swear you're on a tour bus to heaven. The lagos Enol and Ercina are pastoral beauties.

1) Ponferrada/Villafranca del Bierzo/Cebreiro. These places are a microcosm of Spain: Man-made beauty coupled with God's green-earth magnificence. The Templar castle in Ponferrada is the most impressive military structure I've seen just from a size perspective. The entrance is imposing and the vistas from all over stun. Villafranca is an almost untouched medieval town that is larger than other "untouched" villages in the area like Acebo or Molinaseca. Cebreiro has about ten houses and is on the Santiago road, but has that certain "yo no se que" that captivates the soul. I've been known to log onto CRTVG's web cam for Cebreiro and stare for hours at the little hamlet in the mountain pass.

Feliz viaje!