He was then suspected to be behind a plan to kill the King by blowing up the Buen Retiro Palace.
As a punishment, he was sent to Portugal to fight the insurgents, where he was made prisoner after the defeat at Montes Claros.
Gaspar de Haro is buried in the pantheon of the Count-Dukes of San Lúcar and Olivares at Loeches near Madrid.
During his stay in Rome his agent, Antonio Saurer negotiated in Venice the acquisition of important works of art.
He also engaged Bernini to make a copy of the Fontana dei Quattro Fiumi on the Piazza Navona in Rome, to be placed in Naples.He first married Antonia de la Cerda Enríquez de Ribera y Portocarrero, daughter of Antonio de la Cerda, 7th Duke of Medinaceli, deceased in January 1670.