After 1922, Ireland was divided into the predominantly Catholic Republic of Ireland covering five sixths of the island, and Northern Ireland which is predominantly Protestant. The document also describes The Burren region in northwestern Ireland where glaciers 15,000 years ago exposed the flat underlying rock. It mentions the Giant's Causeway in Northern Ireland, a natural formation of hexagonal basalt columns, and Newgrange, an ancient temple in County Meath that receives over 200,000 visitors annually making it Ireland's most visited archaeological site.