(Canto 16, line 94)
The river Montone, running down from the Apennines, in the Romagna region. Dante's geographical specification might be a little confusing and should be understood like this: Mount Viso (Monte Veso), much further to the west, is where the Po, the major northern Italian river, starts, flowing eastwards, and the first river east and south of this point not to join the Po, but to flow directly into the Adriatic Sea, ("holdeth its own course") was the Montone. Today the Montone's course has changed by human intervention and it now joins the Ronco. In its upper reaches, the Montone is known by the name Acquacheta, but when it enters the plain of Forli ("its low bed") it changes this name into Montone. The waterfall referred to here is the Romiti falls, near the monastery San Benedetto dell' Alpe.
Dante's comment "a single leap, where for a thousand there were room enough" has been interpreted as a veiled attack on the monastery mentioned, said to be rich enough to accommodate a thousand monks but only admitting a few. This explanation is however not generally accepted.