With a surface of 56.76 km² it is the second lake by extension in the region (second only to Bolsena) and one of the major lakes of Italy. It has a circular perimeter of approximately 32 km; its surface is 160 meters above sea level and its deepest point is 165 m..
The volcanic origin of the lake is due to intense volcanic activity (from 600.000 to 40.000 years ago) which created many small volcanoes in the Sabatino territory. The main magmatic chamber was situated under the present lake of Bracciano. The sinking in of this chamber created the depression now occupied by the lake. Some small craters are still recognisable around the lake and in the immediate vicinity.
Three towns border the lake, Bracciano, Anguillara Sabazia and Trevignano.
The lake is an important tourist attraction situated near Rome. As it serves as a drinking water reservoir for the town of Rome it is since 1986 under control in order to avoid pollution of its waters. The use of motorboats is strictly forbidden (exceptions for a few professional fisherman and the authorities) and a centralised sewer system has been built for all the bordering towns in order to avoid any spoiling of the water quality. This makes it one of the (if not the) cleanest lakes of Italy. Also the absence of motorized navigation favours sailing and canoeing.
Since a few years the lake and its surroundings have been brought under further protection by the creation of a regional Park called: ”Parco Regionale del complesso lacuale di Bracciano Martignano”.