Name the capital city that serves as the heart of Northern Ireland.

Belfast is the capital of Northern Ireland, and it's been a major port city for centuries. Its history is deeply intertwined with shipbuilding, most famously being the birthplace of the Titanic in the early 20th century. This industry helped Belfast grow rapidly, becoming a significant industrial center. While Northern Ireland is part of the United Kingdom, it has its own distinct identity and administrative structure, and Belfast serves as its political and economic hub, housing the Northern Ireland Assembly. The other cities listed are capitals or major cities in other parts of the UK: Edinburgh is the capital of Scotland, Swansea is a city in Wales, and Glasgow is a major city in Scotland, but none of them have any connection to Northern Ireland's governance. So, if you're thinking about the center of power and administration in Northern Ireland, Belfast is the key city to remember.