ALATRI, DIOCESE of. — In southern Latium, in the province of Frosinone. The see, A., stands on a hill of the Ernici range, near the banks of the Cosa, a tributary of the Sacco. The diocese has 30,000 inhabitants, 16 parishes, 34 diocesan priests and 15 religious priests, 5 male and 9 female religious communities. Patron: s. Sisto I. The bishopric is immediately subject to the Holy See, and its territory borders those of Ferentino and Veroli.
An ancient city of the Ernici, A. preserves an imposing circuit of walls which, in its oldest part, is dated to the 6th century B.C. Together with Ferentino, it remained faithful to Rome during the rebellion of the Ernici in 306 B.C. At the time of the Social War it was made a municipium. Christianity was preached there from the earliest times, but the first bishop of whom there is record is Pascazio, who in 551 accompanied Pope Vigilius to Constantinople. In 680 another bishop, Saturnio, is mentioned in the acts of the Sixth Ecumenical Council of Constantinople. The episcopal succession is intermittent until the age of Gregory VII, and subsequently also presents uncertainties and gaps. Devastated by Totila in the 6th century, its citizens withdrew farther north, founding Collepardo. Shortly afterward A. rose again under the name of Civitanova.
Under Bishop Pietro, on 11 January 1132, the miraculous translation of the body of its patron saint, Sisto I, the pontiff martyred under Hadrian and buried with great honor in the cathedral of S. Paolo, is said to have taken place; there, in 1584, Bishop Ignazio Dandi carried out its discovery and solemn recognition. In 1159 Bishop Adenolfo (or Rodolfo) embraced the cause of Barbarossa and adhered to the imperial antipope, Vittore IV, against Alessandro III; this did not prevent A. from being captured several years later, in 1165, by Cristiano of Mainz. Subsequently it resisted the sieges of Enrico VI (1185) and Federico II (1234).
A town still medieval in appearance, rising on the sides of the Acropolis, upon which the Cathedral stands, it has in the collegiate church of S. Maria Maggiore, with its fourteenth-century tower, in the tower-house of Cardinal Gottifredo, and in the Conti Gentili palace its finest medieval and Renaissance buildings, with numerous works of art and the municipal and chapter archives, the latter especially rich in parchments from the 11th–14th centuries. — Vedi Plates XLIV–XLV.