Lago di Piediluco is a lake that straddles the border between the Province of Terni, Umbria, Italy and the Province of Rieti, Lazio. At an elevation of 375 m, its surface area is 1.58 km². The lake is formed by the inflow of water from three sources: the Rio Fuscello, the Velino river and the Nera river. The flow from the Rio Fuscello is naturally occurring, while the flows from the Nera and Velino rivers are each due in some part to man-made means. A partial diversion of the Nera river in the Nera river valley (Valnerina) conducts the flow via a lengthy aqueduct and canal system built in the 1920s during the fascist regime of Benito Mussolini, entering the lake at the western end of Piediluco near the entrance to the town from the "Via Ternana" SS79 motorway. A canal of approximately 400 meters' length was built, also in the 1920s, to divert the Velino river from its existing natural course into the lake.