This is castlevisitor's daughter, but I'm a castlevisitor too!

I'm planning a long trip to Spain as my Congressional Award Gold Medal Exploration Project. I'm in my fourth year of college Spanish and this is more a cultural exploration than a vacation.
We like castles and historical sites - not really into shopping or beaches when we go overseas. We arrive in Madrid, train to Granada, visit various Andalucian towns, ending in Sevilla for a few days. From there we fly to Santiago de Compostela, drive along northern Spain through Leon, Bilbao, and Cardona to Catalonia where we end with several days in Barcelona.
We plan to visit many of the major sites: the Alhambra, Sevilla's Alcazar, Gaudi's works in Barcelona, and many UNESCO sites. I'm looking for recommendations of hidden gems in any of these areas that you've come across on your travels - things that may not be highlighted in the tour guides that I've been using like Fodor's, DK, Rick Steve's. Thank you for sharing your highlights!

Have you checked Castles of Spain? (http://www.castillosnet.org/spanishc...mapa_index.php)

Some of the following are well known others not.

Cuenca
Ronda
Santillana del Mar
Salamanca
Merida
San Sebastian

Outside of Santiago
Lugo, the only walled city in the world surrounded by intact Roman walls.
Islas Cies near Vigo. Often cited as one of the ten most beautiful beaches.

Don;t miss Merida if you can help it - wonderful Roman remains.

Aduchamp and nytraveler have the right idea, I think. All the places listed are wonderful.

On my last trip, my travel companion, who had never before been to Europe, was so overwhelmed by her first sight of the Roman theater in Mérida that she said she had to fight back tears.

The geology of both Cuenca and Ronda are stunning.

Also add to your possibilities:

The Royal Palace in Aranjuez

http://www.arannet.com/frtourism.htm

Segovia has a castle and Roman acqueduct that they just using about 20 years ago, a beautiful and inspiring structure.

http://www.segoviamint.org/english/segovia.htm

Salamanca has the oldest univeristy in Spain and a stunning Plaza Mayor.

http://en.wikipedia.org/wiki/Salamanca

On your way from Leon to Bilbao, go if you can to the Picos de Europa area, specifically I loved Cangas de Onis and Covadonga, with the lakes of Enol and Ercina up in the mountains. Stunning!

Like most things, you'll find them in some guidebook, but here are two places that may be off the main tourist radar that we really enjoyed on our recent trip to Spain:

Casa Andalusi, C/ Judios 12, Cordoba. This is a lovely little 12thc house built around a central courtyard; it's part store, part museum; supposedly also a tearoom, but I didn't see any evidence of that. You visit five or so ground floor rooms of the house, the central courtyard brimming with wonderful plants, and two smaller courtyards at the side, and the basement with roman mosaic.

Palacio de la Condesa de Lebrija, Sevilla. An amazing house, formerly owned by what sounded like an amazing woman. Roman mosaics throughout the house (taken from the nearby former Roman city of Italica), some of which you actually walk on, plus amazing mudejar style throughout. I would call this a "must-see," especially for anyone interested in history and the art and architecture.

You may want to take a look at my blog as a local on the BAsque Country for off the beaten track places, there´re a couple of castles mentioned

http://www.blogseitb.us/basquetouris...tle-of-butron/

http://www.blogseitb.us/basquetouris...wer-of-varona/

there are also suggestions for places on your route. Hope you find it useful!

Check La Calahorra in Granada province, there'sa a beautiful castle there.

This was a fun question, here are some ideas:

ANDALUCÍA
Antequera is known as "the heart of Andalucía" or "the crossroads of Andalucía". Almost right in the middle of the Sevilla, Córdoba, Granada, Málaga rectangle. Here you'll find dolmens (some 5000 years old burial chambers), Roman baths, a Moorish Castle, Gothic churches, Renaissance fountains and baroque bell towers. Antequera was the first of the Granada emirate towns to fall to the Christians in 1410.
http://www.andaluciacoastandcountry.com/antequera.html

I love the terrace in the corner of the peaceful square in front of the Real Colegiata de Santa María la Mayor, the first partly Renaissance-style church in Spain (built 1514-1550). Up here it's totally peace and quiet. Next to the recently excavated Roman baths beneath and looking up on the 13th century Moorish alcazaba/fortress. Great views over unique landscapes (the spectacular Torcal limestone mountain etc.). Had the concert experience of my life up here a few years ago. http://www.wild-about-travel.com/201...ing-antequera/

Antequera is also the site of a an Andalusian Muslim Christian version of a Romeo and Juliet legend, ending tragically at the so called Peña de los enamorados/Lover's rock just outside town: http://www.spain-holiday.com/blog/th...-antequera.php

When in Sevilla you should see the ruins of the Roman city Itálica. 10 mins and 20€ by taxi or frequent buses from the Plaza de las Armas bus station. The allegedly most successful and competent of all the Roman emperors, Trajan, was born here. A fine tapas bar/restaurant right in front of the entrance:
http://en.wikipedia.org/wiki/Italica

And perhaps visit the recently resuscitated ghost village Acebuchal between Granada and Málaga? http://fincafantastica.biz/article-s...t-village.html

MADRID
Alcalá de Henares is just outside Madrid. The birthplace of Cervantes (today a museum), and a World Heritage site since 1998. The University of Alcalá, founded in 1499, is one the best conserved Renaissance university complexes in Europe. And in Alcalá, even the McDonald's on the main square looks classy. http://whc.unesco.org/en/list/876

The Madrid terror bombings of 2004 ocurred on three commuter trains from Alcalá when arriving at Madrid Atotcha station in the morning of 11th of March (11M). Monuments to commemorate the victims have been raised in both the Alcalá de Henares and the Atocha train stations.

A lovely small theater in the centre of town - Corral de Comedias - dating back to Cervantes days (1601). The best dancers and musicians perform here on a regular basis. http://www.corraldealcala.com/elcorral/historia.php

In Madrid itself, relax in the heart of Moorish Madrid, one of the most beautiful places in the city: The Vistillas park next to the Almudena cathedral and the Royal Palace. http://www.gomadrid.com/sights/city-walls.html

Here you'll have magnificent views to the sunset over the Guadarrama mountain range (from the terrace at Restaurante El Ventorillo). Map, video and some photos: http://11870.com/pro/restaurante-ventorrillo

BILBAO
Gernika/Guernica is very close to Bilbao. Destructed by German bombers on the 26th of April 1937 during the Spanish Civil War (Picasso's painting). http://en.wikipedia.org/wiki/Guernica_(painting)
Picasso and Guernica: http://www.pbs.org/treasuresofthewor...n_guerfrm.html

Perhaps go a bit inland to the old university town Oñati and the Arantzazu Monastery?
http://en.wikipedia.org/wiki/O%C3%B1ati
http://en.wikipedia.org/wiki/Sanctuary_of_Arantzazu

FINALLY
...speaking of UNESCO, flamenco was put on the immaterial world heritage list last year. I strongly recommend you to experience this beautiful, cathartic and visceral art. In no particular need of protection, but you should know where to go to see the real deal. Madrid, Sevilla, Granada and, yes, Barcelona have got great flamenco venues with performances most days.

In the following places only top artists perform, and a visit in either of them should at least give you a glimpse of what flamenco at its finest can be:

Casa Patas in Madrid (I saw this Concha Jareño performance this summer): http://www.youtube.com/watch?v=95ORMp_E2AY

Casa de la Memória in Sevilla: http://www.casadelamemoria.es/

Peña Flamenca La Platería in Granada, the oldest exisiting flamenco club in Spain. Performances only at Thursdays and some Saturdays. Here, the extremely popular singer Diana Navarro from Málaga. She is not a traditional flamenco singer, but she has a beautiful voice and are fully capable of creating magic: http://www.youtube.com/watch?v=qgPrfjinEgQ

Tablao Cordobés or Tablao de Carmen in Barcelona. Here excellent El Junco, one of my favourite male dancers: http://www.youtube.com/watch?v=sENoCuTQYPs

Then there's Toledo, Segovia, Avila, the Alcazaba in Malaga, Teruel, Roman ruins in Tarragona, the Mezquita in Cordoba, even the Gypsy caves in Sacromonte in Granada are fascinating to me, so many incredible historical sites in Spain.

What an amazing wealth of information you all are! Thank you so much for responding with so many great ideas! I am looking into every one of your ideas and hope that we will have time to see them all. We don't leave until May so if any other special relatively-unknown places come to you, I'd love to hear about them. Thank you again for sharing your love of Spain with me.

Though not a cultural sight in the traditional sense of the word, Casa Hernanz is unique. While known for its espadrilles, they have hemp products all varieties (no not that.) I was once waiting in line and the fellow in front of me bought rope the thickness of which they moor large ships.

http://travel.nytimes.com/2005/06/05...5foraging.html

I think you garnered such a welcomed reponse because of your genuine interest and enthuiasm.

Egbert embodies the essence of the Spain struck spirit!

May is a great time of year to go, full spring blossom both in the South and the North, the South is not too hot and the majority of tourists are yet to invade even the most beaten tracks.

Spain is serious festival turf, and most of the festivals goes way back in time and are primarily local events.

In May, Andalucian towns - especially Granada and Córdoba - celebrate the "Cruces de Mayo": http://www.spanish-fiestas.com/spani...es-de-mayo.htm

Córdoba in May is something special, the "cruces" celebration is followed by the patio competition leading on to the flamenco inspired Feria by the end of the month.
Córdoba patio exposition and competition: http://www.andalucia.com/cities/cordoba/patios.htm
The Feria in late May: http://www.andalucia.com/festival/co...pring-fair.htm

If you go to Córdoba, perhaps also visit the ruins of the 10th century palace city Madinat al-Zahra just outside town? http://www.andalucia.com/magazine/en...d4/madinat.htm

May is also the month of the famous Jerez horse fair and the San Isidro festival in Madrid.
Feria de Caballo de Jerez: http://www.andalucia.com/festival/jerez-horse-fair.htm
San Isidro in Madrid: http://www.madrid-guide-spain.com/san-isidro.html

Useful links:
http://www.spainisculture.com/
http://www.spain.info/en/

And when in Bilbao, perhaps visit the Butrón castle some 20 miles out of town:
http://www.blogseitb.us/basquetouris...tle-of-butron/