In Naples he fomented a conspiracy among the feudal lords, who were discontented with the centralized government established under the auspices of Frederick's chancellor, Piero della Vigna.
His Apologeticus, a defence of the papal claims against the Empire, written - as is supposed - in refutation of Piero della Vigna's argument in favour of the independence of the Empire, has been lost.
Other noteworthy tombs are those of the Granduca, with a single subterranean chamber carefully constructed in travertine, and containing eight sarcophagi of the same material; of Vigna Grande, very similar to this; of Cone Casuccini (the ancient stone door of which is still in working order), with two chambers, containing paintings representing funeral rites; of Poggio Moro and Valdacqua, in the former of which the paintings are almost destroyed, while the latter is now inaccessible.
Thus the title was borne by Pietro della Vigna, the all-powerful minister of the emperor Frederick II., king of Sicily.
Originally erected in 1557 for the use of the Jesuits, the university buildings are regarded as the best work of Marco di Pino; the quadrangle, surrounded by a simple but effective peristyle, contains statues of Pietro della Vigna (Frederick's chancellor), Thomas Aquinas and Giordano Bruno.