Shannon

The ruins of the monastery at Clonmacnoise lie in the valley of the Shannon, south of Athlone in central Ireland. Founded in the 6th century by St Ciarán, it was a centre of learning as well as theology, and the burial site of several local high kings.

Longest river in Ireland, rising 105 m/344 ft above sea level in the Cuilcagh Mountains in County Cavan, and flowing 386 km/240 mi to the Atlantic Ocean past Athlone, and through loughs Allen, Boderg, Forbes, Ree, and Derg. The estuary, which is 110 km/68 mi long and 3–16 km/2–10 mi wide, forms the northern boundary of County Limerick. The river is navigable as far as Limerick city, above which are the rapids of Doonas and Castletroy. The river is known for its salmon farms, Castleconnell being an important centre. It also has the first and largest hydroelectric scheme in the Republic of Ireland (constructed 1925–29), with hydroelectric installations at and above Ardnacrusha, 5 km/3 mi north of Limerick.