After Vignola's death (1573) this Lombardy-born architect became the leading exponent of Mannerism in Rome. He supervised the building of Michelangelo's buildings on the Capitoline Hill, completing (with some changes) the Palazzo dei Conservatori (1561–84) and building the Palazzo del Senatore (1573–1602). His intervention also included modifications to the Piazza and to the great flight of steps. He finished Vignola's noble church of Il Gesù, designing the façade (1571–3) which was to be of enormous importance as a precedent for Jesuit churches in Italy, Central Europe, and Latin America. The great barrel-vault (1577) was his design too. As Architect of St Peter's from 1573, he built the western arm of the crossing, the minor domes (1578–85), and Michelangelo's designs for the elevation to the garden. He collaborated with Domenico Fontana on the building of the great dome (1586–92) to which he gave a more pointed profile (like that at Florence Cathedral) than that intended by Michelangelo. He also completed the chapels of Gregory XIII (1572–85) and Clement VIII (1592–1605).
He designed the north and south fountains in the Piazza Navona (1574–8) and many other Roman fountains, the Church of Santa Maria ai Monti (from 1580), the façades of San Luigi de' Francesi (1580–4) and (probably) Santissima Trinità de' Monti (c.1583), the naves of San Giovanni de' Fiorentini (1582–1602) and Sant'Andrea della Valle (1591—completed by Maderno, 1608–23), and the Villa Aldobrandini, Frascati (1594–1603—completed by Maderno and G. Fontana). His output was enormous, and he is of singular importance as a transitional figure between the Cinquecento and the evolution of Baroque.
Ackerman (1986);Heydenreich (1996);Lotz (1977);P. Murray (1969, 1986);Onofrio (1957, 1963);Placzek (ed.) (1982);Tiberia (1974);Jane Turner (1974);Wittkower (1964, 1982)