The River Shannon is 360 kms (224 miles) and is by far the longest river in Ireland and is named after the Celtic goddess, Sionna. It’s source is the Culicagh Mountain in Co. Cavan (Maybe!) and it then flows through 11 counties towards the Shannon Estuary in Limerick. The river is relatively slow moving as it only falls 60 feet in the first 150 miles of its course. It is the natural divide for 3 of Ireland’s provinces with Connacht to the west and Leinster and Munster to the east and south.