≈ 14 km
Isola del Liri and the Great Waterfall
The historic centre stands on an island formed by the Liri. At the Boncompagni-Viscogliosi Castle the river divides: the left branch forms the Cascata Grande, a vertical drop of about 27 metres right in the town centre; the right branch forms the Valcatoio waterfall, which runs down a slope.
The castle, owned by the Della Rovere family, passed in 1579 to Giacomo Boncompagni, son of Pope Gregory XIII, and became the seat of the Duchy of Sora. It is privately owned and can be visited by appointment.
In the 19th century the power of the water made Isola the paper-making centre of the Kingdom of Naples, with paper and wool mills. Buildings and machinery remain today as industrial heritage.
The best viewpoint is Ponte Napoli, on Corso Roma. In the evening the waterfall is lit up.