Shannon River Basin a measurement of . When added to the Shannon's estuary this gives a total river flow of , which makes it the longest river within the River Shannon basin (from source to mouth)— longer than the Shannon Pot source. Thus the Boyle-Shannon river can be regarded as having the longest natural river flow in Ireland. The River Shannon Basin touches more than half (17) of Ireland's counties:- Limerick, Clare, Tipperary, Offaly, Westmeath, Longford, Roscommon, Kerry, Galway, Leitrim, Cavan, Sligo, Mayo, Cork, Laois, Meath and Fermanagh. There are many towns situated in the Shannon Basin. Towns and Villages (with 2011 populations)
County Offaly Mountain which are the county's second and third highest peaks. Croghan Hill rises from the Bog of Allen and is located in northern Offaly. Although only 234 metres high, it is known for its view over the surrounding area and it stands out by itself. The floodplain of the River Shannon is in the north-western part of the county. The River Camcor runs through the town of Birr and is a Wild Trout Conservation Area. The River Brosna runs across the county from Lough Owel in Westmeath to Shannon Harbour. Silver River runs through several towns in the south of