The palazzo was purchased by Cardinal Spada in 1632. He commissioned the Baroque architect Francesco Borromini (佛朗西斯科·博罗米尼) 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 lifesize 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. (http://en.wikipedia.org/wiki/Palazzo_Spada)
这个弧形的过道仅有8米长， 看上来像是37米长。雕塑仅有0.6米高， 看上来像是6米高。
