The area around the lake was conquered by the Romans in the same period as  Perugia. Trasimeno is first noted in Roman history with the struggle of 217 BC, when the army of Hannibal destroyed the legions and 25.000 soldiers died among the hills of Tuoro and the banks of the lake.

Romans left to the Trasimeno the sign of its great hydraulic science with the building of the first outlet aimed at regulating of the level of waters and at avoiding the floods, by anticipating a technology which was subsequently repeated from Braccio Fortebraccio up to present times. The settlement structure preserved in the Park is today mainly the medieval one with the castles, the fortified centers of Passignano, Monte del Lago, and Castiglione del Lago.

From the lake sheet of water, three islands rise: the Polvese - 64,4 Ha - which belongs to the Provincial Administration, the Maggiore - 23,2 Ha - still permanently inhabited, and the Minore - 6,5 Ha - abandoned and part of an entirely natural surrounding.

The Park around the lake  is the instrument to protect and at the same time exploit the Trasimeno Lake, the largest lake of the Italian peninsula with a surface of 128km/q, a little less than the Como Lake.
Besides the sheet of water, the Park includes all the bank system surrounding it, and therefore also the small and big historical centers like Castiglione del Lago and Passignano.