As a cardinal, Alessandro had begun construction of the Palazzo Farnese in central Rome, and its planned size and magnificence increased upon his election to the papacy. The palace was initially designed by the architect Antonio da Sangallo the Younger, received further architectural refinement from Michelangelo, and was completed by Giacomo della Porta. Like other Farnese family buildings, the imposing palace proclaims the family's power and wealth, similarly to Alessandro's Villa Farnese at Caprarola. In 1546, after the death of Sangallo, Paul appointed the elderly Michelangelo to take supervision of the building of St. Peter's Basilica. Paul also commissioned Michelangelo to paint the 'Crucifixion of St. Peter' and the 'Conversion of St. Paul' (1542–50), his last frescoes, in the Pauline Chapel of the Vatican.