Spain

From Madrid, Going northwest toward Salamanca, Zamora, Valladolid (and castles around Valladolid area), Burgos, Bilbao, San Sebastian/Donostia, Pamplona (and nearby Olite for the small castle there), Zaragosa, then back to Madrid would be a nice loop. Add or subtract stops based on your available time. If you have time to add you could expand west, to Santiago de Campostello or east, to Barcelona (I'd choose the latter first). If you need to lose time, go back to Madrid after Bilbao. Good luck with your Spanish. I really speak more of a Mexican dialect (but studied Castilian). I didn't hear proper Spanish until about 20 days into a thirty day trip, and that was from a Bodega tour guide in Jerez. Up north they speak Basque (Vasco?), in Barcelona they speak Catalon. Even in the Castille areas, most people spoke something similar to Castilian - but not really proper Castilian. Spain is great, enjoy your trip.

Cantabria on the coast - Santander is beautiful. Also Bilbao, and that area in general. Salamanca, and Zamora - the childhood home of El Cid. Be sure to see the Caves of Altmira, north of Santander.