TUSCANIA, DIOCESI di. — In Latium, in the province of Viterbo, united with the diocese of Viterbo (v. , also for the statistical data). T. stands on the slope of a tuffaceous hill; of Etruscan origin, it later became a Roman municipium and, when the Papal State was established, enjoyed considerable importance until the 13th century. Around 1130 it took the name of Toscanella, which it retained until 1911.
Evangelical preaching in T. must have taken place after the Constantinian peace, even if the names of martyrs venerated there might suggest otherwise. A Passion (BHL, 7550), composed in Rome, most probably between the 5th and 6th centuries, recalls Veriano, Marcellino, and Secondiano as buried in S. Pietro of T. and says that all three were from Rome. Other martyrs, also venerated in T., have an obscure history, such as Tesidio (1 Apr.), Potente (7 Dec.), and Giustina (23 Dec.). The oldest Christian inscription found in the church of S. Pietro dates from 407 (CIL, XI, 1, 2994–95). The first in the series of known bishops is Virbonus, in 595. In the 11th century, the bishoprics of Civitavecchia and Bieda seem to have been subject to the episcopal see of T. In 1192 Celestine III Viterbo (v.) and united T., Civitavecchia, and Bieda to it, so that from then on the bishops were called bishops of Viterbo and T.: this must have occurred between Aug. and Oct. of that year, because in Aug. Cardinal Giovanni of S. Clemente still signed himself bishop of T., whereas on 4 Oct. he signed himself bishop of Viterbo and T. It cannot be denied that, with the establishment of the see of Viterbo, T. passed into second place, above all because of the importance that the city of Viterbo came to assume, where the bishops gradually established their permanent residence. The oldest documents preserved in the archives of T. bear the dates 1086 and 1097.
Among the ancient monasteries of the Tuscanese territory, of which only the ruins remain today, mention should be made of the Benedictine monastery of S. Giusto, very close to T., which in the 12th century passed to the Cistercians; that of S. Savino, over which the abbey of Cluny exercised jurisdiction in the 10th century; and that of S. Stefano on the island of Martana in Lake Bolsena, already known from a privilege granted by Leo IV to Bishop Virbono of T. between 847 and 855. By contrast, S. Maria Maggiore and S. Pietro, near the carriage road at the edge of the built-up area of T., are preserved and considered the most beautiful Romanesque churches in Latium. S. Maria Maggiore was also the first cathedral of T.; it was later transferred to S. Pietro, and in 1572 to the church of S. Giacomo. The two aforementioned churches display their architectural development from the 8th to the 13th century, but they must have replaced pre-existing places of worship.
T. is immediately subject to the Holy See and has its court of appeal at the vicariate of Rome. — Vedi tav. XLIV.