The Alcázar de los Reyes Cristianos, also known as the Alcázar of Córdoba, is a medieval alcázar located in the historic centre of Córdoba, next to the Guadalquivir River and near the Mosque-Cathedral. The fortress served as one of the primary residences of Isabella I of Castile and Ferdinand II of Aragon. It is a building of military character whose construction was ordered by the King Alfonso XI of Castile in the year 1328, on previous constructions.