Fontana, Domenico (dōmĕˈnēkō fōntäˈnä) [key], 1543–1607, Italian architect. He went to Rome, where he built (c.1580) the Sistine Chapel in the Church of Santa Maria Maggiore for Cardinal Peretti. When his patron was made pope (Sixtus V), Fontana played a leading part in the great rebuilding of Rome. He designed the Lateran palace (1588) and portions of the Vatican, notably the library (1588). An engineer as well as an architect, he built, with his brother Giovanni, the great aqueduct and fountain known as the Acqua Felice (1587) and in 1586 erected the obelisk in front of St. Peter's, a feat that won him wide renown. With Giacomo della Porta, he completed the dome of St. Peter's. On the death of Sixtus V, Fontana's Roman career collapsed; he withdrew to Naples, where he built the imposing royal palace (1600) and where he died before the execution of his magnificent designs for the improvement of the harbor.