The Italian architect Giacomo della Porta (ca. 1537-1602) was the leading Roman architect in the last quarter of the 16th century.

It was formerly thought that Giacomo della Porta was a Lombard, like many of the artists active in Rome in the 16th century, and that he was related to the sculptor Guglielmo della Porta. His earliest biographer, however, stresses that Giacomo was Roman "by birth and by skill," and this is now accepted as correct, especially as his career was crowned by his appointment as "architect to the Roman people."

Della Porta may have been apprenticed to Giacomo da Vignola, whose Roman career began about 1550, but he first emerges as a follower of Michelangelo. Della Porta designed the central window of the Palazzo dei Conservatori on the Capitol (ca. 1568) after Michelangelo's death, but it is so fantastic that it surpasses even Michelangelo's daring inventions, and for this...