Lake Bracciano has a surface area of 57 sq. km and a 32 km perimeter, and is the second largest lake in Lazio after Lake Bolsena. It covers a group of craters of the ancient Sabatine volcanoes. It is circular and fed by a number of small rivers including two underwater tributaries from the little lakes of Martignano and Stracciacappe. Nowadays the downflow is regulated by a dam, but in periods of high water the overflow spills into the Arrone River which flows into the Tyrrhenian Sea at Fregene. The northern shores are rocky and wooded while those in the south are marshy. Lakeside towns include Bracciano, Vicarello (and nearby, Bagni di Vicarello, whose bicarbonate, sulphurous and alkaline thermal waters are used to treat rheumatic diseases), Trevignano Romano and Anguillara Sabazia.

The lakeside towns are linked by good roads.