In 1540, the palace was commissioned by Cardinal Girolamo Capodiferro, and utilized as an architect Bartolomeo Baronino of Casale Monferrato, while Giulio Mazzoni and a team provided lavish external and internal stucco-work. The palace was briefly owned by the Mignanelli family, until in 1632, the palace was purchased by Cardinal Spada, who commissioned modifications from Francesco Borromini. The Baroque architect Borromini who created a masterpiece of forced perspectiveoptical illusion in the arcaded courtyard, in which diminishing rows of columns and a rising floor create the visual illusion of a gallery 37 meters long with a life-size sculpture at the end of the vista, in daylight beyond: the sculpture is 60 cm high. Borromini was aided in his perspective trick by a mathematician. The Manneriststucco sculptural decor of the palazzo's front and its courtyard façades feature sculptures crowded into niches and fruit and flower swags, grotesques and vignettes of symbolic devices in bas-relief among the small framed windows of a mezzanine, the richestcinquecento façades in Rome. The colossal sculpture of Pompey the Great, erroneously believed to be the very one at whose feet Julius Caesar fell, was discovered under the party wall of two Roman houses in 1552: it was to be decapitated to satisfy the claims of both parties, which appalled Cardinal Capodiferro so, that he interceded on the sculpture's behalf with Pope Julius III, who purchased it and then gave it to the Cardinal. The palazzo hosts the Galleria Spada, the Cardinal Spada's collection, which includes four galleries of 16th and 17th-century paintings by Andrea del Sarto, Guido Reni, Titian, Jan Brueghel the Elder, Guercino, Rubens, Dürer, Caravaggio, Domenichino, the Carracci, Salvator Rosa, Parmigianino, Francesco Solimena, Michelangelo Cerquozzi, Pietro Testa, Giambattista Gaulli, and Orazio and Artemisia Gentileschi, and has the additional interest of being hung in the 17th-century manner, frame-to-frame, with smaller pictures "skied" above larger ones. Palazzo Spada was purchased by the Italian State in 1927 and today houses the Italian Council of State, which meets in its richly frescoed and stuccoed rooms.
