CASTLES OF SPAIN - Arévalo Castle, Avila. In 1462 the possession of the castle, together with the title of Duke, was given to Don Alvaro de Zuñiga, count of Plasencia, by King Enrique IV. Don Alvaro is the builder of the castle we see today. During the reign of the Catholic Kings Isabel and Fernando (15th/16th century), the castle became a state prison. A Dutch Prince, Philip William of Orange-Nassau has been a prisoner here in the 16th century.