Interior view

The Palazzo Spada was originally built in 1540 for Cardinal Girolamo Capodiferro. Bartolomeo Baronino (1511-1554), of Casale Monferrato, was the architect, while Giulio Mazzoni (c. 1525-c. 1618) and a team provided lavish stuccowork inside and out.

The palazzo was purchased by Cardinal Spada in 1632. He commissioned the Baroque architect Francesco Borromini to modify it for him, and it was Borromini who created the masterpiece of forced perspective optical 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 (it is 8 meters) 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 picture shows the forced perspective gallery by Francesco Borromini. The corridor is much shorter, and the sculpture much smaller, than they appear.