Ireland - Dublin - the Brazen Head is the oldest pub. Facts of Ireland: Area: 70,285 sq km. Comprises 80% of the island of Ireland. Northern Ireland is a constituent part of the United Kingdom. Population: 4,589,002. Capital: Dublin. Official language: Irish, English. Irish spoken as a first language by less than 4% of the population; 40% of the Irish population can speak Irish. Languages: 5.