The United Kingdom of Great Britain and Northern Ireland is a sovereign state off the north-western coast of continental Europe. It spans an archipelago including Great Britain, the northeastern part of the island of Ireland, and many smaller islands. Northern Ireland is the only part of the UK with a land border with another sovereign state, sharing it with the Republic of Ireland. Apart from this land border, the UK is surrounded by the Atlantic Ocean, the North Sea, the English Channel, and the Irish Sea. London is its capital city.