(LAGO FUCINO, or LAGO DI CILANO), in Ancient Geography, a lake in the country of the Marsi. Strabo describes it as being like a sea in size; and it was undoubtedly the largest body of fresh water in Central Italy; but its circumference does not exceed thirty miles. It is surrounded on all sides by mountains (one of which, Monte Velino, attains a height of more than 8000 feet), and does not appear to have any natural outlet. Its elevation above the sea-level is 2176 feet. Its eastern and western boundaries are limestone ridges of considerable height; on its north-western side it is separated by a gentle slope from the channel of the Salto, a tributary of the Tiber. Several curious traditions are current regarding the Lake Fucinus. One of these is to the effect that it was traversed by a river called the Pitonius, whose waters did not mix with those of the lake. This story appears to have had its origin in the fact that the surplus waters of the lake were carried off by a subterranean channel, the opening of which, still visible, is now called "La Pedogna," a manifest derivative from Pitonius. As the channel, however, was not wide enough to carry off all the surplus water, especially after the heavy rains, the low grounds round the shores of the lake were frequently flooded. One of these floods is said to have engulfed the town of Archippe, and the neighbouring inhabitants had a tradition that when the waters were low the remains of that town might be traced beneath the waves. To prevent the devastation and loss of life consequent upon these inundations, Julius Caesar formed the great design of cutting a subterranean canal from the lake to the valley of the Liris or Garigliano. Death frustrated this design, which none of his successors had leisure or inclination to carry out before Claudius. That emperor cut a gallery of 15,600 English feet through Mount Salviano; a work of great labour, from the hardness of the limestone rock, and which is said to have occupied 30,000 workmen for eleven consecutive years. This gallery, which is reckoned by Pliny one of the most memorable proofs of Roman greatness, was allowed to fall into decay, and it was gradually choked up with stones and rubbish falling from above.

All the efforts that have been made to clear it since the middle of the thirteenth century have not hitherto been wholly successful. Much of the best land in the Abruzzo has consequently been swallowed up. In 1830, however, the king of the Two Sicilies caused some important repairs to be executed on it, which have had the effect of obviating the risk of future inundations. A company was formed at Naples in 1852 to drain the entire lake, which according to a recent official survey covers 36,315 acres. This company does not yet appear to have commenced operations.