of the area of Ulster is in the UK while the remaining 38% is in the Republic of Ireland. Ulster's biggest city, Belfast, has an urban population of over half a million inhabitants, making it the second-largest city on the island of Ireland and the 10th largest urban area in the UK. Six of Ulster's nine counties, Antrim, Armagh, Down, Fermanagh, Londonderry and Tyrone, including the former parliamentary boroughs of Belfast and Londonderry, form Northern Ireland which remained part of the United Kingdom after the partition of Ireland in 1921. Three Ulster counties – Cavan, Donegal and Monaghan – form part of the Republic of Ireland. About half of Ulster's population lives in counties Antrim and Down. Across the nine counties, according to the aggregate UK 2011 Census for Northern Ireland, and the ROI 2011 Census for counties Cavan, Donegal and Monaghan, there is a Roman Catholic majority over Protestant of 50.8% to 42.7%. While the traditional counties continue to demarcate areas of local government in the Republic of Ireland, this is no longer the case in Northern Ireland. Since 1974, the traditional counties have a ceremonial role only. Local government in Northern Ireland is today demarcated by 11 districts. County-based sub-divisions Counties shaded in grey are in the Republic of Ireland. Counties shaded in pink are in Northern Ireland. Council-based sub-divisions Largest settlements Settlements in Ulster with at least 14,000 inhabitants, listed in order of population: Belfast (480,000) Derry (105,000) Lisburn (75,000) Craigavon (65,000) Bangor (58,400) Ballymena (28,700) Newtownards (27,800) Newry (27,400) Carrickfergus (27,200) Coleraine (25,000) Antrim (20,000) Omagh (19,800) Letterkenny (19,600) Larne (18,200) Banbridge (14,700) Armagh (14,500) Economy The GDP of the province of Ulster is around €50 billion. Salary levels are the lowest on the island of Ireland. Physical geography The biggest lake in the British Isles, Lough Neagh, lies in eastern Ulster. The province's highest point, Slieve Donard (), stands in County Down. The most northerly point in Ireland, Malin Head, is in County Donegal, as are the sixth-highest () sea cliffs in Europe, at Slieve League, and the province's largest island, Arranmore. The most easterly point in Ireland is also in Ulster, in County Down, and the most westerly point in the UK is in County Fermanagh. The longest river in the British Isles, the Shannon, rises at the Shannon Pot in County Cavan with underground tributaries from County Fermanagh. Volcanic activity in eastern Ulster