The predominant religion in Ireland is Christianity, with the largest church being the Roman Catholic Church. Ireland's constitution states that the state may not endorse any particular religion and guarantees freedom of religion.
The Republic of Ireland is divided into 30 administrative regions, mostly tied to the 26 constituent counties (county Tipperary is divided in two and county Dublin in four).
The main river in Ireland is the River Shannon, 386 km (240 mi), the longest river in either Ireland or Great Britain, which separates the boggy midlands of Ireland from the West of Ireland. The river develops into three lakes along its course, Lough Allen, Lough Ree, and Lough Derg. Of these, Lough Derg is the largest.