A dam is built on the river after the confluence with the Sacco river, its main tributary, at Ceprano. The last important tributary of the Liri is the "Melfa", with which it joins near Aquino. The river forms the border between Lazio and Campania regions and, after Cassino, it joins the "Gari" river and then it is known as "Garigliano". After , the river flows into the Tyrrhenian Sea.