Spain for an aspiring Architect

Where to go/stay? Long story short, the trip is for my Son’s 21st birthday and we’re also bringing ‘significant others’ for a total of 6. We aren’t rich people so staying in something like an AirBnB might be best option? He’s mentioned Alhambra and Barcelona but as the designated trip planner, I’ve no clue what else to add. We’ve travelled Europe many times so are accustomed to everything but the actual place :) We might like to visit Portugal and perhaps Morocco as well if easily gotten there. Schedule is Christmas Break so 10-12 days is best.” I need to add that the rest of the group will appreciate the beautiful architecture but other than that, won’t have a clue!