It is the second river of Southern Italy due to its volume of water. The Sele (64 km) rises on the north-eastern part of the Monte Plafagone (foothill of the Cervialto), at an altitude of 420 meters, in the district of Caposele.

Its main source, like that of the Calore, feeds the Apulian Aqueduct, the initial section of which, with the historic tunnel, wooden structures, and original valves, is located and can be visited in Piazza Sanità in Caposele. Since 1909, when this mammoth and futuristic hydraulic engineering feat was completed, much of the water flowing from the Paflagone spring has been destined for consumption in Puglia, where the Campanian river quenches the thirst of four million people, reaching the Adriatic Sea via the aqueduct at Santa Maria di Leuca.

On its upper reaches in Irpinia area, it receives numerous torrents and valleys. Its tributary is the river Acquabianca (6 km), which rises in the Monti Picentini, crosses the natural oasis Valle della Caccia and which, after a spectacular waterfall, it joins the Sele in the district of Senerchia. The Sele keeps its way southward entering in the Cilento.