Lake Iseo, also called Lake Sebino, stretches from the mouth of the Camonica Valley, where the most southerly spurs of the Bergamo and Brescia Alps are separated from the upland plain. It is the fourth biggest of the Italian Prealpine lakes with a surface area of 65 sq. km, 25 km long and 4.7 km at its widest. It is formed by the River Oglio which flows from the Camonica Valley in the north, runs into the lake between Lovere and Pisogne, and then flows out again near Sarnica in the south west. It is also fed by the waters of the Tinazzo, the Trobiolo and the Bagnadore. The island of Montisola, 4 sq. km and 415 m high, is the biggest lake island in Italy and is situated in the middle of the lake. Olives, vines and orchards indicate the mildness of the climate which produces luxuriant growth. The two longest sides of the lake are very steep and give the landscape an Alpine appearance. On the eastern, Brescia side, rocky cliffs drop steeply into the water, while the eastern bank, on the Bergamo side, is slightly less inhospitable and full of little bays. Little health resorts are dotted here and there along the banks and the most popular are Iseo, Pisogne, Lovere, Sarnico and Monte Isola (on the island of the same name).

Excellent roads connect Bergamo and Brescia to the lake and go all round the lake. Regular ferry services connect the lakeside towns.