224th Pope of the Catholic Church. Pontificate 1559 - 1565. Pius IV was a nepotist. Among the relatives he favored, the main figure is that of Carlo Borromeo. Under his reign Michelangelo re-built the basilica of Santa Maria degli Angeli (in the Diocletian's Baths) and the eponymous Villa Pia, now known as Casina Pio IV and headquarters of the Pontifical Academy of Sciences, was designed by Pirro Ligorio in the Vatican Gardens.