One thing that stands out about Belfast is the number of churches and in some areas I noticed at least two or thee on every street that I visited. As far back as 1861 there were 55 Churches in Belfast 20 Presbyterian, 20 other non-conformist 10 Church Of Ireland and 5 Catholic. Today it is not clear as to how many churches exist in Belfast but there is a large number [some claim that there are more than 1,000 which is unlikely to be true as that would be equivalent to one for every 700 people] of small churches with very small congregations. I suspect that many of the churches are not currently viable and are likely to cease within the next ten years.
If you are wondering what I mean by a small congregation I extracted the following from the Moravian Church web page "our communicant membership stands at 60 with a few adherents and several people who attend occasionally".
Christianity is the main religion in Northern Ireland. The 2011 UK census showed 40.8% Roman Catholic, 19.1% Presbyterian Church, with the Church of Ireland having 13.7% and the Methodist Church 3.0%. Members of other Christian churches comprised 5.8%, 16.9% stated they have no religion or did not state a religion, and members of non-Christian religions were 0.8%.
The Roman Catholic Church is the largest single church, though there is a greater number of Protestants overall. The Catholic Church in Ireland is organised into four provinces though these are not coterminous with the modern political division of Ireland. The seat of the Archbishop of Armagh, the Primacy of Ireland, is St. Patrick's Cathedral, Armagh.
The Presbyterian Church in Ireland, closely linked to the Church of Scotland in terms of theology and history, is the second-largest church and largest Protestant denomination. It is followed by the Anglican Church of Ireland, which was the state church of Ireland until it was disestablished by the Irish Church Act 1869. In 2002, the much smaller Methodist Church in Ireland signed a covenant for greater co-operation and potential ultimate unity with the Church of Ireland. The Church of Ireland is part of the Anglican Communion.
Smaller, but growing, Protestant denominations such as the Free Presbyterian Church of Ulster, Reformed Presbyterian Church of Ireland amongst Presbyterians and the Open Brethren are located in many places. The Association of Baptist Churches in Ireland and the Assemblies of God Ireland are also organised on an all-Ireland basis, though in the case of the Assemblies of God this was the result of a recent reorganisation.
In their respective 2011 censuses Northern Ireland had a lower proportion of people stating that they were Christian (82.3%) than the Republic of Ireland (90.4%) and had a higher proportion of people stating that they had no religion or not indicating a religious belief (16.9%) than the Republic of Ireland (7.6%). While in the 2011 census 84.2% of people in the Republic of Ireland identified themselves as Catholic in the 2011 census in Northern Ireland only 40.8% identified themselves as Catholic.