Lake Como is fed mainly by the Adda River, which enters the lake near the town of Colico and leaves in Lecco.

There is only one island in the lake - Isola Comacina - which was inhabited in ancient times, but the existing settlements there were destroyed in the 12th century.

The lake is divided into three parts: Ramo di Como, Lago di Lecco, and Ramo di Colico.