Pedro IV´s palace is a unique example of architecture in Aragon. Pedro IV commissioned  Blasco Aznárez Borau, architect of the reform of the Aljaferia of Saragossa, to build this palace. Its construction dates from the mid-fourteenth century, when the fortress of Uncastillo had two towers of more than twenty meters high and with the Gothic palace, which became a strong symbol in the north of Zaragoza.