The Garda Lake is the biggest of Italy, and the southern part is reachable through the A4 highway and the train line that connects Milan and Venice.
You can't miss:
Sirmione, a marvellous village on a peninsula with a Medieval Castle, Roman Ruins, beaches and spas.
Salò, a small town on the west montainous bank, and the Vittoriale degli Italiani National Monument (https://www.vittoriale.it/en), former residence of the poet and adventurer Gabriele d'Annunzio.
Vittoriale Panoramic Picture
Peschiera, a the fortified town with a channel port. Not so far Gardaland amusement park. (https://www.gardaland.it/en/)
Desenzano, with a long promenade on the lake.