Domenico Fontana
The facade, with its rhythm of flat doubled pilasters between the arch-headed windows, is Florentine in conception, comparable to Leone Battista Alberti's Palazzo Rucellai. The overall pattern of drafted masonry, cut with smooth surfaces and grooves around the edges, is ancient Roman in origin. The grand portal was added in the 16th century by Domenico Fontana on the orders of Cardinal Alessandro Farnese.