Lake Iseo (or Sebino) is of glacial origin, located in the Pre-Alps at the bottom of Val Camonica, between the provinces of Brescia and Bergamo, its level is regulated by the Sarnico dam, built in 1933 in Fosio. Since 2018, the northern portion of the lake, called Alto Sebino, has been part of the UNESCO biosphere reserve of "Valle Camonica - Alto Sebino". With a maximum depth of 251 meters, it is the fifth deepest lake and the seventh largest lake in Italy. The main tributaries are Oglio and Borlezza rivers; the main emissary is Oglio river, in the southern part of the lake between Paratico and Sarnico.

Lake Iseo is characterized by the presence of the largest natural lake island in Italy as well as the highest lake island in Europe with its 600 meters above sea level, Monte Isola, and two islets, one located north of the last one, Loreto island, and one further south, San Paolo island.