Lake Fondi (Italian: Lago di Fondi, Latin: Lacus Fundanus, Lacus Amyclanus) is a brackish lake about 90 km (56 mi) to the southeast of Rome in the Province of Latina, Lazio, Italy, in the region called Sud or "South" Pontino, the western end of which is the Piana di Fondi, "Plain of Fondi". The plain is a basin below the arc of the Monti Ausoni and the Monti Lepini. The lake forms naturally at the west end of the basin in a depression constantly filling with spring water exuding from the base of the mountains, which are a heavily cracked and faulted limestone karst absorbent of most rainfall. In addition to the flows from springs, a number of canals have been constructed from regions of the marsh below sea level to drain water from the marsh into the lake. Pumping stations are required to lift the water into the canals. Before the marsh was reclaimed the lake was part of it.