He belonged to a family perhaps of Lombard origin, but that worked mainly in Rome, he probably spent part of his youth (1565-70) in Genoa, engaged along with D. Scorticone in the works for the completion of the Annunziata's façade, in which some of Vignola's prospects for the façade of the Gesù in Rome were carried out. What's certain is that his fecund production is entirely inspired to Michelangelo's and Vignola's architectonic schemes, yet harmonized with a highly original plastic sense that rightfully attributes to Della Porta a pre-eminent position in the formation of the late sixteenth century taste. To him we owe the cupola and façade of the Gesù; by inserting in this last one a balcony window, he introduced in the rigorous geometric quality of Vignola's original project a freer and more open vision in the quest for scenographic solutions. An equal search for picturesque rhythms can be perceived in the façade of S. Luigi dei Francesi, in two superimposed planes separated by a simple crowning fronton and varied by the alternated triangular and curved tympanums that frame the doors and the windows. As Vignola's successor, together with Domenico Fontana he completed Michelangelo's project for St. Peter's cupola; that was vaulted with an slightly higher outer line therefore different from the semi-circular profile conceived by Michelangelo. These are the major works of the Lombard maestro; but also the other (churches of the Madonna dei Monti and of S. Atanasio dei Greci in Rome and of S. Sinforosa in Tivoli; completion of Palazzo Farnese in Rome; mayor's palace in Velletri; villa Aldobrandini in Frascati; prospect and courtyard of La Sapienza in Rome; completion of the Campidoglio's arrangement ; etc.) reveal just how great were his abilities of accomplisher, if not as an innovator.