Ireland is predominantly a rural island, with a generally low density of population and indeed few large towns other than those situated on the coast. The regional geography of the island is simpler than that of Great Britain, and especially than the regional geography of England.

The Central Plain of Ireland stretches west-east across the country from coast to coast. Glacial action has created hollows, enlarged by solution of the underlying limestone by rain water, and many shallow lakes have been formed. A large proportion of Ireland’s terrain consists of either bleak and uninhabitable mountain masses, or valleys and lowlands containing large loughs, innumerable smaller sheets of water, and great peat bogs that are useless except as a source of fuel. Lough Derg, on the River Shannon, is narrow, irregular, and nearly forty kilometres in length.

Around the plain is a broken rim of mountains. In the extreme north-east is the Antrim Plateau or Mountains of Antrim, which rise above 400 m and are composed of basalt. Off the north coast is the famous Giant’s Causeway, where the basalt solidified in remarkable hexagonal columns. In the north and northwest are the Sperrin Mountains and the Ox Mountains, which with several other uplands reach more than 500 m in height. The loftiest mountains of Ireland are in the south-west — the Macgillycuddy Reeks, which contain Carrantouohill (1,041 m), the highest peak on the island. In the south-east the Wicklow Mountains rise to 926 m in Lugnaquillia. They form one of the most extensive masses of granite in the British Isles. And in the north-east there are the Mourne Mountains which rise steeply from Carlingford Lough to reach a height of 852 m in Slieve Donard.

Being geographically an island and a single unit, Ireland is politically divided into the Irish Free State and Northern Ireland, or Ulster, comprising today six counties: Antrim, Londonderry, Tyrone, Fermanagh, Armagh and Down.