In the southern Apennines, to the south of the Sangro valley, the three parallel chains are broken up into smaller groups; among them may be named the Matese, the highest point of which is the Monte Miletto . The chief rivers on the south-west are the Liri or Garigliano with its tributary the Sacco, the Volturno, Sebeto, Sarno, on the north the Trigno, Biferno and Fortore.