Lake Garda is the largest lake in Italy.
The northern part of the lake is narrower, surrounded by mountains, the majority of which belong to the Gruppo del Baldo. The shape is typical of a moraine valley, probably having been formed under the action of a Paleolithic glacier. Although traces of the glacier's actions are evident today, in more recent years it has been hypothesised that the glacier occupied a previously existing depression, created by stream erosion 5 to 6 million years ago.
The lake has numerous small islands and five main ones, the largest being Isola del Garda where in 1220 St. Francis of Assisi founded a monastery, in its place now stands a nineteenth-century building in the Venetian Gothic style. Nearby to the south is Isola San Biagio, also known as the Isola dei Conigli ("Island of the Rabbits"). Both are offshore of San Felice del Benaco, on the lake's western side. The three other main islands are Isola dell'Olivo, Isola di Sogno, and Isola di Trimelone, all farther north near the eastern side. The main tributary is the Sarca River, others include the Ponale River (fed by Lago di Ledro), the Varone/Magnone River (via the Cascate del Varone) and various streams from both mountain sides, while the only outlet is the Mincio River (79 metres (259 ft), at Peschiera). The subdivision is created by the presence of a fault submerged between Sirmione and Punta San Vigilio which is almost a natural barrier that hampers the homogenization between the water of the two zones.