With its stuccoed ornamental facade and handsome courtyard, this grand palazzo is a fine example of 16th-century Mannerist architecture. Upstairs, a small four-room gallery houses the Spada family art collection with works by Andrea del Sarto, Guido Reni, Guercino and Titian, while downstairs Francesco Borromini's famous optical illusion, aka the Prospettiva (Perspective), continues to confound visitors.
The Prospettiva appears to be a 25m-long corridor lined with columns leading to a hedge and life-size statue but is, in fact, only 10m long. The sculpture, which was a later addition, is hip-height and the columns diminish in size not because of distance but because they actually get shorter. And look closer at that perfect-looking hedge – Borromini didn’t trust the gardeners to clip a real hedge precisely enough so he made one of stone.