Ireland is an island in the North Atlantic, separated from Great Britain to its east by the North Channel, the Irish Sea, and St George's Channel. Politically, the island is divided between the Republic of Ireland, a sovereign state, and Northern Ireland, which is part of the United Kingdom. Dublin is the capital and largest city of the Republic. The island's geography is characterized by central plains surrounded by a ring of coastal mountains. It is famously called the 'Emerald Isle' because of its lush green landscape, a result of the frequent rainfall and mild climate influenced by the North Atlantic Current. One of its most famous geological features is the Giant's Causeway in Northern Ireland, consisting of about 40,000 interlocking basalt columns. The coastline is rugged, featuring the dramatic Cliffs of Moher on the western edge facing the Atlantic Ocean. Ireland is also known for its extensive peat bogs and numerous lakes (loughs).