1911 Encyclopædia Britannica/Trasimene, Lake
TRASIMENE, LAKE (Lat. Trasumenus Lacus; Ital. Lago Trasimeno), a lake of Umbria, Italy, 12 m. W. from Perugia, 843 ft. above sea-level, 50 m. in circumference, and 8 m. to 14 m. across. Having no natural outlet, it was formerly subject to sudden rises, which occasioned inundations, and these in turn malaria. An artificial outlet was completed in 1898 from the south-east corner of the lake to the Caina, a small tributary of the Tiber. The work, which is about 4 m. long, cost only about Â£26,000. It is intended to leave about 2500 acres of land dry, and to convert another 2800 acres of marshy soil into cultivable land. The lake contains three small islands: Isola Maggiore, with a monastery, Isola Minore and Isola Polvese. Standing on a promontory jutting out into the lake is the town of Castiglione del Lago, which possesses a castle of the dukes of Cornia, built by Galeazzo Alessi, the architect of many of the Genoese palaces. Napoleon I. formed a project for draining the lake, which may ultimately be adopted. Here Hannibal disastrously defeated the consul C. Flaminius. Hannibal left his winter quarters in Cisalpine Gaul in the spring of 217 B.C. and crossed the Apennines, probably by the pass now known as the Passo dei Mandrioli (from Forli to Bibbiena in the upper valley of the Arno). His march was much hindered by marshes (probably those in the Arno valley between Bibbiena and Arezzo). The Roman army under Flaminius was stationed at Arezzo (anc. Arretium), and Hannibal marched past it. Flaminius followed, and Hannibal occupied the heights on the north of the lake between Terontola and Tuoro, commanding the road from Cortona to Perugia, and also those on the east of Tuoro, so that when the Roman army (which had encamped the night before outside the entrance to the small valley of the brook now called Sanguineto, west of Tuoro), unable in the mists of early morning to see the enemy's forces, had entered the valley, it was surrounded and there was no escape except by forcing a passage. The vanguard succeeded in making their egress on the east by Passignano, but the defeat of the rest of the army was complete, the Romans losing no fewer than 15,000 men.
See T. Ashby in Journal of Philology (1908), and refs.