[2] The palace lies east of the southernmost of the two propylaea erected by Marcello Piacentini in 1950 to frame the view of Piazza Pio XII which is the forecourt to Saint Peter's Square.

[5] Armellini was indirectly responsible of the Sack of Rome in 1527, since in 1525 he unwisely advised the Pope to discharge almost all his soldiers, leaving the city almost without defense.

[5] On 6 May 1527, the Landsknechts of Holy Roman Emperor Charles V burst into the city pulling down a wall of his palace's garden while he was trying to bury there his jewels and the treasure of the pope.

Angelo Cesi, bishop of Todi, and his brother Pier Donato took charge of the restructuring, relying for the new project on Martino Longhi the Elder, who between 1570 and 1588 oversaw the renovation into its present form.

[10] In 1939, during the works for the opening of Via della Conciliazione, the palace, which until that time had its main front on the Borgo Vecchio road, escaped destruction, but was modified according to a project of Marcello Piacentini and Attilio Spaccarelli.

[10] These had been hidden there by the second superior general of the Salvatorians, father Pancrazio Pfeiffer, who was also instrumental in the decision to declare Rome an open city.

[13] The main portal, which was moved during the reduction of the façade from 12 to 8 bays, is flanked by two Doric pillars, and bears an entablature with metopes composed with architectonic elements of the Cesi family.

[13] The upper façade shows exposed bricks, and is chanted by double lesenes, which divide it in squares containing the windows, whose frames bear the inscription P.DONATUS.CAR.CAESIUS., Pier Donato Cesi's name in Latin.