Lake Trasimeno, also called Lake Perugia, is the biggest lake in central Italy and the fourth biggest in Italy as a whole. It has a surface area of 128 sq km and its perimeter is 54 km long. It is entirely within Umbria in the province of Perugia. Its origins being principally alluvial and only partly tectonic, it is supplied mainly by rainwater. It is also fed by a number of small rivers in its modest catchment basin and by springs which bubble up from the bottom of the lake. It has no natural outlet but is connected to the Tiber by a canal built by the Romans and frequently restored since. The lake is well stocked fish. Of its three islands, Maggiore Island and Minore Island are near the north shore, while the largest, Polvese Island, is near the south-west shore. Amongst the main towns on the lakeside are Castiglione del Lago, on the west side, and Passignano on the north side.
A ferry service operates between Passignano, Tuoro, Maggiore Island and Castiglione.