Terni (anc. Interamna Nahars), a town, episcopal see, and the seat of a sub-prefecture of the province of Perugia, Italy, situated among the Apennines, but only 426 ft. above sealevel, in the valley of the Nera (anc. Nar), from which the town took its distinguishing epithet, 5 m. below its junction with the Velino, and 70 m. N. by E. of Rome by rail. Pop. (1906) 20,230 (town), 33,256 (commune). It has important iron and steel works and iron foundries, at which armour-plates, guns and projectiles are made for the Italian navy, also steel castings, machinery and rails, a royal arms factory, and lignite mining. Terni lies on the main railway line from Rome to Foligno and Ancona, and is the junction for Rieti and Sulmona. Its most interesting buildings are the cathedral (17th century, with remains of the earlier 13th century facade), the church of S. Francesco (partly dating from the 13th century, with some frescoes of the 14th), and other old churches. Its antiquities include traces of the city walls of rectangular blocks of travertine, remains of an amphitheatre of the time of Tiberius, a temple, theatre and baths (?), and numerous inscriptions. Remains have also been found of a pre-Roman necropolis. The excavations and the objects found are described by A. Pasqui and L. Lanzi in Notizie degli scavi, 9 7, 595 seq. Five miles to the east are the falls of the Velino (Caseate delle Marmore). Alike in volume and in beauty these take a very high place among European waterfalls; the cataract has a total descent of about 650 ft., in three leaps of 65, 330 and 190 ft. respectively. They owe their origin to M'. Curius Dentatus, who in 272 B.C. first opened an artificial channel by which the greater part of the Lacus Velinus in the valley below Reate was drained. They supply the motive power for the factories of the town.
Terni is the ancient Interamna (inter amnes, " between the rivers," the Nar and one of its branches), originally belonging to Umbria, and founded, according to a local tradition preserved in an inscription, in the year 672 B.C. It is first mentioned in history as being, along with Spoletium, Praeneste and Florentia, portioned out among his soldiers by Sulla. Its inhabitants had frequent litigations and disputes with their neighbours at Reate in connexion with the regulation of the Velinus, the waters of which are so strongly impregnated with carbonate of lime that by their deposits they tend to block up their own channel. The first interference with its natural course was that of M'. Curius Dentatus already referred to. In 54 B.C. the people of Reate appealed to Cicero to plead their cause in an arbitration which had been appointed by the Roman senate to settle disputes about the river, and in connexion with this he made a personal inspection of Lake Velinus and its outlets. In the time of Tiberius there was a project for regulating the river and its outlets from the lake, against which the citizens of Interamna and Reate energetically and successfully protested (Tac. Ann. i. 79). Similar questions arose as the river formed fresh deposits during the middle ages and during the 15th and 16th centuries. A branch of the Via Flaminia passed from Narnia to Forum Flaminii, and is given instead of the direct line in the Antonine and Jerusalem itineraries. A road led from here to the Via Salaria at Reate. Interamna is also mentioned in Cicero's time as being the place where Clodius wished to prove that he was on the night when he was caught in Caesar's house at the celebration of the rites of the Bona Dea. The Emperor Tacitus and his brother Florianus were probably natives of Interamna, which also has been claimed as the birthplace of Tacitus the historian, but with less reason. During most of the middle ages and up till 1860 Terni was subject to the popes. It was the scene of the defeat of the Neapolitans by the French on the 27th of November 1798.
