Ireland Geographical Facts, Figures and Physical Extremities

Most northerly point*	The most northerly point is Inishtrahull Island, situated in the Atlantic Ocean 7 km north of Inishowen Peninsula, county Donegal. It lies at latitude 55.43ºN. Of mainland Ireland, the most northerly point is a headland 2 km northeast of Malin Head, Inishowen Peninsula, county Donegal. It lies at latitude 55.38ºN.
Most easterly point	The most easterly point is Big Bow Meel Island, which is a rock situated 900 metres off the Ards Peninsula, county Down, at longitude 5.42ºW. Of mainland Ireland, the most easterly point is Burr Point, Ards Peninsula, county Down at longitude 5.43ºW. It is situated 2 km southeast of the village of Ballyhalbert.
Most southerly point	The most southerly point is Fastnet Rock, which lies in the Atlantic Ocean 11.3 km south of mainland county Cork. It lies at latitude 51.37ºN. Of mainland Ireland, the most southerly point is Brow Head, county Cork, which lies 3.8 km east of the marginly more northerly Mizen Head. It lies at latitude 51.43ºN.
Most westerly point*	The most westerly point is Tearaght Island, which lies in the Atlantic Ocean 12.5 km west of Dingle Peninsula, county Kerry. It lies at longitude 10.70ºW. Of mainland Ireland, the most westerly point is Garraun Point, Dingle Peninsula, county Kerry which is 2.5 km northwest of Slea Head. It lies at longitude 10.51ºW.
Geographical Centres	The geographical centre of Ireland is to be found in eastern county Roscommon, at a point 3km (2 miles) south of Athlone town. The centre of Ulster is in county Tyrone, at a point 20km (14 miles) east of Omagh town, near the village of Pomeroy. The centre of Munster is in the north of county Cork, at a point 9km (6 miles) south-west of the village of Rath Luirc. The centre of Leinster is in western county Kildare, at a point 5km (3 miles) south-west of Kildare town. The centre of Connaught is in county Mayo, 6km (4 miles) south-east of the pilgrim village of Knock. The centre of Northern Ireland is in eastern county Tyrone, at a point 6km (4 miles) south-east of the town of Cookstown. The centre of the Republic of Ireland is in south-eastern county Galway, at a point 3km (2 miles) south-west of the village of Eyrecourt.
Highest altitude	The summit of Mt Carrantuohill, county Kerry, rises to 1,041 metres (3414 feet) above sea level. The second highest point is the summit of Mt Beenkeragh, county Kerry, which rises to 1,010 metres (3314 feet) above sea level. The highest point in Northern Ireland is the summit of Slieve Donard, county Down, which rises to 852 metres (2796 feet) above sea level, and is the 8th highest peak in Ireland.
Tallest sea cliffs	The sea cliffs at Croaghaun, Achill Island off western Ireland fall 668 metres (2,192 feet) into the Atlantic Ocean. Slieve League in county Donegal has a drop of 601 metres (1,972 feet) into the same ocean. Both cliffs are almost twice the height of the Eiffel Tower in Paris. However, as there is no vantage point to see the cliffs at Achill Island the Donegal cliffs are more famous. (thanks to Michele of irelandyes.com for this information)
Most populated county	The most heavily populated county is county Dublin, with 1,056,666 inhabitants at the last estimate. The next most heavily populated county is Antrim, with 566,400 inhabitants.
Most densely populated county	The most densely populated county is county Dublin, with 1147.3 inhabitants per square kilometre at the last estimate. The next most densely populated is county Antrim, with 199.2 inhabitants per square kilometre.
Least populated county	The county with the fewest inhabitants is county Leitrim with just 25,032 inhabitants at the last estimate. The next lowest is county Longford with 30,128 inhabitants.
Most sparsely populated county	The most sparsely populated county in Ireland is Leitrim, with a mere 15.8 inhabitants per square kilometre at the last estimate. The next most sparsely populated is county Mayo, which has 19.9 inhabitants per square kilometre.
Largest settlements	The largest city in Ireland is Dublin, which at 859,976 inhabitants, is home to almost 1 in 5 Irish people, and more than 1 in 4 in the Irish Republic. The next 9 largest settlements are Belfast (counties Down and Antrim, 475,968), Cork (county Cork, 174,400), Limerick (county Limerick, 75,436) Derry (county Londonderry, 72,334), Newtownabbey (county Antrim, 56,811), Dún Laoghaire (county Dublin, 55,540), Bangor (county Down, 52,437), Galway (county Galway, 50,853) and Lisburn (county Antrim, 42,110). More towns.
Largest county	In terms of area, the largest county in Ireland is county Cork at 7,457 km². The next largest is county Galway, at 6,148 km². The largest county in Northern Ireland is county Tyrone, at 3,155 km².
Smallest county	The smallest county in Ireland is county Louth, which is just 820 km² in area - 9 times smaller than county Cork. The next smallest is county Carlow, which is 896 km². The smallest county in Northern Ireland is county Armagh, at 1,254 km².
Longest river	The longest river in Ireland is the river Shannon whose source is Shannon Pot, county Cavan, and which enters the sea between counties Clare and Limerick after a journey of 386 km (240 miles). It is, in fact, the longest river in the British Isles. The longest river within Northern Ireland is the river Bann, whose source is in the Mourne Mountains, county Down and which enters the sea in county Londonderry after 122 km (76 miles).
Largest lake	Lough Neagh, Northern Ireland, which is 396 km² (153 miles²) in area. It forms part of counties Tyrone, Londonderry, Antrim, Down and Armagh. It is, in fact, the largest lake in the British Isles.
Closest to Britain	The closest point that Ireland comes to Britain is Torr Head, county Antrim, which is just 23 km (14 miles) from the Mull of Kintyre, Scotland. On most days, fields in Scotland can be seen clearly across the North Channel.
Largest island	Besides Ireland itself (82,463 km²) the largest offshore island in Irish waters is Achill island, county Mayo, with an area of 148 km² (57 miles²).
Tallest waterfall	Ireland's tallest waterfall is Powerscourt Falls, county Wicklow, where the water drops 106 metres (350 feet). It is the third tallest waterfall in the British Isles.
Sunniest town	The town in Ireland which enjoys the most sunshine is Rosslare, county Wexford which has over 1600 hours of sunshine per year (4 hrs, 20 mins per day).
Cloudiest town	The town in Ireland which receives the least sunshine is Omagh, county Tyrone which has less than 1200 hours of sunshine per year (3 hrs, 20 mins per day).
Wettest place	The wettest place in Ireland is the area of the Maumturk and Partry mountains of counties Mayo and Galway, which receive annually over 2400 mm of rain.
Driest place	The driest place in Ireland is Dublin city which receives less than 800 mm of rain per year.