Paul began the famous Villa Borghese; enlarged the Quirinal and Vatican; completed the nave, facade and portico of St Peter's; erected the Borghese Chapel in Sta Maria Maggiore; and restored the aqueduct of Augustus and Trajan ("Acqua Paolina").
Early in the year the crown prince Humbert with the Princess Margherita took up their residence in the Quirinal Palace, which, in view of the Vatican refusal to deliver up the keys, had to be opened by force.
Incensed by the elevation to the rank of embassies of the Italian legation in Paris and the French legation to the Quirinal, and by the introduction of the Italian bill against clerical abuses, the French Clerical party not only attacked Italy and her representative, General Cialdini, in the Chamber of Deputies, but promoted a monster petition against the Italian bill.
From early times he was worshipped at Rome on the Quirinal hill, whither, according to tradition, a body of Sabines under Titus Tatius had migrated from Cures and taken up their abode.
He painted the "Battle of Joshua" in the Quirinal Gallery, the "Crucifixion of St Andrew" in the church of that saint on Monte Cavallo, various works for the Jesuits, some also in co-operation with his brother.