SEGNI, DIOCESE OF. – A city and diocese in the province of Rome, 58 km distant from it, at an elevation of 665 m above sea level. It has an area of 250 sq km and a population of 32,000, all Catholic, distributed among 14 parishes served by 35 diocesan priests and 10 regular clergy; it has a seminary, 3 male religious communities and 11 female ones (Ann. Pont. 1932, p. 373). It is immediately subject to the Holy See. The diocese’s patron is St Bruno.
It is the ancient Signia, in a strong strategic position on the obligatory route for the Hernican peoples toward Rome. The ancient tradition, preserved by Livy, recalls it as a colony of Latin right. The people of Signia remained always faithful to Rome, even during the Hannibalic War. The name *opus signinum* is given to a special waterproof plaster made with crushed tiles bound with local mountain lime. Segni still preserves almost the entire circuit of its cyclopean walls, about 2 km longer than the perimeter of the present city, which constitute an example of exceptionally strong city and acropolis defenses; they are the most imposing in Latium: notable is the Saracen Gate, which has the special feature of narrowing toward the top and of supporting five enormous monoliths. Because of its position and fortifications, Segni was not much damaged during the period of the invasions; in the Byzantine period it was part of the Duchy of Rome; in the early years of the 8th century it passed to the Church; then, in 1333, to the family of the Counts of Segni; subsequently, by marriage, it came to the Sforzas as a fief; it was raised to a duchy in 1639; then acquired by the Barberinis, it returned to the Sforzas and finally to the Sforza-Cesarinis. In 1557, during the war between Pope Paul IV and Philip II of Spain, it was sacked by the Spanish troops of the Duke of Alba because the inhabitants of the neighboring villages had gathered there.
Christianity was preached in Segni from the earliest centuries; the city was already a episcopal see in the 5th century. The first bishop of whom we have record is Saintulus, who was present in Rome at the Council of Symmachus in 499; but, prevented from attending, he had the decrees signed by Fortunatus, bishop of Anagni. He is followed by Bishop Justus, who subscribed to the 3rd Roman Synod of 501, the 4th of 502, and the 6th of 504. Of the greatest importance in the history of the Church of Segni is St Bruno of Solero (Alessandria [v.]). Lucius III, with the letter *Et ordo rationis expostulat* of 4 November 1182, addressed to Bishop Peter (appointed by Alexander III and present at the Lateran Council)