A historical and topographical excursus of the city of Naples is followed by a small treatise on heraldry and the history of 33 noble Neapolitan families of Roman origin. Born in Naples on 25 July 1575 into a bourgeois family, De' Pietri had a refined education, first in the humanities under the guidance of Cesare Vetta, and then in law with Giulio Berlingieri and Alessandro Turamini. But it was above all the originality of his historical thinking which, free from academic conventions, played no small part in preparing and bringing about the Neapolitan revolution of 1647-48. His most important work: "Dell' Historia Napoletana" actually constitutes the response of the "civilized" class to the absolutist policy of the Madrid court. Weak from a philological point of view, the work had an entirely political value: it was the interpreter of a widespread anti-Spanishism and of a republicanism which, if latent in the culture of the time, the latest events had revived and brought out into the open as a practicable solution institutional. And, between the lines, the possibility emerged that the government was exercised by a Senate, the expression of all the elites.