Situated in the far south of Umbria on the border with Lazio, sitting tight between the Luco and Caperno mountains it is the largest in the region after Trasimeno. It has a regular basin and for this reason features an extensive shoreline of approx. 13 km, in respect to its surface of only 1.52 sq. km.
It lies 370 mt asl, and reaches a maximum depth of around 20 mt. near the inhabited centre so there are not many places where the water is deeper than 12 mt. Among the main inlets is the Rio Fuscello that originates from the eastern slope of the Tillia, the other two are artificial canals. Piediluco Lake, together with the smaller ones of the Rieti plain, are all that remain of the ancient Lacus Velinus, originally alluvial, formed starting from the Quaternary as a consequence of orohydrographic events of the Nera and Velino rivers. It was thought that the Velino Lake at its largest extension practically covered the entire Rieti plain stretching as far as the border with Marmore.
Piediluco is the only village overlooking the lake. A small village of medieval origin, although archaeological excavations brought to light settlements dated as far back as the late Bronze age. Among the most significant monuments is the Fortress (XIII century) and the Church of Saint Francis (XIII century).