Ireland enjoys a temperate maritime climate, due mainly to its proximity to the Atlantic Ocean and the presence of the Gulf Stream. Known as the Emerald Isle, Ireland is so green because it receives a lot of precipitation.
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.
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.