Eric, what kind of trip interests you? Culture and art? History? Moorish architecture? Great food and wine? Outdoor adventure? All of the above? My husband and I just returned from 2 weeks in Spain, starting in Barcelona and ending in Madrid, visiting Toledo (2 nights there), Sevilla (2 nights) Granada (3 nights) and Cordoba (1 night) in between. We are in the "all of the above" category and our expectations were not only met but exceeded. We traveled entirely by train and it was perfect. The Spanish train system is wonderful (and I'm used to Switzerland so this is saying a lot). If you purchase your tickets in advance on the Renfe website and get the Web discounts (60% off) the train is also very reasonable priced. Of course you could not visit all of these places in 10 days, but you could easily visit Madrid (3 nights), Toledo (one night, I agree with HJ), 3 nights in Sevilla/Cordoba OR Granada, and 3 nights in Barcelona. If you are interested in seeing the Alhambra, then Granada would be the natural choice. However, it is a bit out of the way, and not on the high-speed train route. The regular trains go to Granada from Madrid, but to get from there to Barcelona is difficult unless you fly. The budget airlines make this very doable. If on the other hand you choose Sevilla and/or Cordoba, these are a short ride from Madrid by high-speeed AVE train. And the train between Madrid and Barcelona takes only 3 hours.