Too many great options to choose from. We chose Toledo. Very convenient train ride - the Regional express train out of Atocha (in Madrid) took only an hour each way. Were told the bus station was more convenient, but found a taxi from Toledo train station to central Toledo was only 600psts (3-4 Euros?). For me, Toledo was exciting to experience the history of
three (!!!) "civiliztions" (Moors, Jews, and Christians), at one time coexisting with each other. I'd say my vote is for Toledo for the convience and cultural experience - it's a biased vote, though, as I havn't been to the others.