The Litani River cuts through a deep gorge directly below Beaufort Castle, and the valley scenery is a significant part of the attraction of visiting Arnun. The river is Lebanon's largest, rising in the Beqaa Valley and turning sharply westward before reaching the sea south of Sidon. The stretch below the castle is particularly dramatic — the gorge is steep and the water fast-moving after the winter rains.
From the castle walls you can look down several hundred metres to the river. The surrounding hills are terraced with tobacco and olive plantations, and on a clear day the view extends westward over the coastal plain to the sea. The valley also contains several bridges and fords that have been strategic crossing points since antiquity — part of what made Beaufort Castle's position so valuable.