South of Palestrina again, the main mass of the Apennines throws off another lateral mass, known in ancient times as the Volscian mountains (now called the Monti Lepini), separated from the central ranges by the broad valley of the Sacco, a tributary of the Liri (Liris) or Garigliano, and forming a large and rugged mountain mass, nearly 5000 ft.
Several of the Latin cities, including Tibur and Praeneste, were situated on the terrace-like underfalls of these mountains, 2 while Cora, Norba and Setia were placed in like manner on the slopes of the Volscian mountains (Monti Lepini), a rugged and lofty limestone range, which runs parallel to the main mass of the Apennines, being separated from them, however, by the valley of the Trerus (Sacco), and forms a continuous barrier from there to Terra.cina.
The most healthy portions of the territory are in the north and east, embracing the slopes of the Apennines which are watered by the Teverone and Sacco; and the most pestilential is the stretch between the Monti Lepini and the sea.
Too a considerable proportion of the group of the Lepini belongs to the province.
They are traversed by three principal valleys: (I) that of the Anio, now called Teverone, which descends from above Subiaco to Tivoli, where it enters the plain of the Campagna; (2) that of the Trerus (Sacco), which has its source below Palestrina (Praeneste), and flows through a comparatively broad valley that separates the main mass of the Apennines from the Volscian mountains or Monti Lepini, till it joins the Liris below Ceprano; (3) that of the Liris (Garigliano), which enters the confines of New Latium about 20 m.