The industrial development of Terni in the second half of the 19th century is strictly linked with water, especially with the use of the net of channels from the Nera River and its tributaries. The Nerino channel was very important because in Italy it was the first facility created specifically for industrial purpose. It permitted very easy access to and exploitation of water from the Nera River. The big factories located in the valley needed increasing amount of water to maximize their productivity; as a result, many hydroelectric power plants were built. With their plants and facilities, they have deeply changed the landscape of Terni. The industrial settlements, often of grand sizes, are so striking that this area is one of the most important itinerary of industrial archaeology, full of ruins and sedimentation of some of the most significant industrial examples in Italy, mostly in the iron and steel, chemical and electric sectors. In fact, in Terni more than elsewhere the abandoned industrial areas are indelible marks on a territory where ruins of the ancient productive machinery are often strongly bound up with the modern industrial world, creating a place where past and present coexist.
The itinerary includes factories located inside and outside town, result of constant changing in functions (not only production), that after their abandonment have undergone many vicissitudes. The plant of the Siri, that produced synthetic ammonia and made research and experimentation, was built in Terni, in a large area near the inhabited centre on the left side of the Nera River. It occupies the site that in 1794 was owned by the Papal ironworks. The complex is interesting because it shows the different development of productive, representative and housing functions. More than half complex has been demolished in the ‘90s to build houses and then it became property of the Comune di Terni, which has redeveloped it. Since 2009 it houses the CAOS, Centro Arti Opificio Siri.
The calcium carbide factory in Papigno was located among the inhabited centre of Papigno and the surrounding area of the mountains Valle and Sant’Angelo. The area presents an extraordinary concentration of building, quarries and pipeline transports. A possible reuse of the wide complex, now abandoned, has been discussed for decades, both for its purpose and the costs. Collestatte Piano, in Collestatte, is an example of reuse of an industrial plant for housing purpose. After its abandonment, the area of the calcium carbide factory was partially demolished and partially used to create houses for workers or warehouses. The area is functional to the needs of tourist flows to the near Marmore Falls. The plant of the Officine Bosco, that produced iron and steel to build machineries, was located near the North wall of Terni. Since its demolition in 1985, the ruins have been transformed in a Multimedia Area that shares the wide space of the former plant with a school and a big parking lot.