midway between Perugia and Trasimeno, formerly an island in the lake. The first civilization to inhabit this area was the Etruscans; three of the main Etruscan cities - Perugia, Chiusi, and Cortona - are within of the lake. Little physical evidence remains from the period of Etruscan or later Roman settlement. Castiglione del Lago has some Roman ruins and its main streets are structured like a chessboard in the Roman style. The Battle of Lake Trasimeno occurred on the northern shore of the lake in April 217 B.C. during the Second Punic War. The exact location of the battle is unknown because the lake then extended further north; the battle could have been fought between Cortona and Tuoro. Near Cortona is a place called 'Ossaia', in Italian meaning ossuary. Another place with reference to the battle is the place named Sanguineto, whose name is connected with the Italian term sangue meaning "blood" or, probably, "bloody place." Local climate The Trasimeno climate is fairly warm, with moderate winters. Summers can be very warm and humid, but in general the lake moderates the climate both in cold and warm conditions because even shallow water gives a moderate thermic inertia. From May to September, the temperature is high enough to allow swimming. In 1929, a cold winter froze the whole of the lake's surface, and cars could be driven over the ice. Cold winters in 1957, 1985 and 2002 caused heavy damage to the olive trees nearby. A less severe freeze happened in 1991. Given the latitude of the lake, freezing remains a rare occurrence. Water level The water level of the lake is very dependent on the amount of seasonal rain and can change significantly from one year to the other. The water level is usually at its minimum level after summer (in September or October) and at its highest during spring (in April or May). Trasimeno has high hills to the east, which help to capture rain and partially protect the lake from cold eastern winds. Most of the water in the lake comes from the network of streams on the western side of the lake. The reference water level of the lake is set at 257.33 AMSL. This level corresponds to a maximum depth of around 6m. Actions are planned to reduce the water level when it climbs above 257.60 AMSL, but since the maximum level was set the lake