The Preapennines of Latium, marked by the Tiber valley and the Liri with the Sacco tributary, include on the right of the Tiber, three groups of mountains of volcanic origin: the Volsini, Cimini and Sabatini, whose largest former craters are occupied by the Bolsena, Vico and Bracciano lakes. To the south of the Tiber, other mountain groups form part of the Preapennines: the Alban Hills, also of volcanic origin, and the calcareous Lepini, Ausoni and Aurunci Mountains. The Apennines of Latium are a continuation of the Apennines of Abruzzo: the Reatini Mountains with Terminillo (2,213 m), Mounts Sabini, Prenestini, Simbruini and Ernici which continue east of the Liri into the Mainarde Mountains. The highest peak is Mount Gorzano (2,458 m) on the border with Abruzzo.