The origins of this castle, called "de la Mota" because of its site on a small raised mound overlooking the town, go back to the 12th century, when it guarded a fortified town within the Kingdom of Castile, on the frontier with León. Its present form, however, is the result of alterations carried out in the 15th century, from the reign of John II (reigned 1406-1454) onwards. In 1475 it passed into the hands of the Catholic rulers Ferdinand and Isabella. During their reign new work was carried out under the direction of Alonso Nieto with the collaboration of Moorish architects such as masters Abdallah and Alí de Lerma. In the 16th century the fortress was converted into a state prison; prisoners included Cesare Borgia and Hernando Pizarro.