Belfast (Irish Béal Feirste) is the capital and largest city of Northern Ireland. Historically most of it is in County Antrim west of the River Lagan, with about a third on the east bank in County Down; but it's always been governed as a separate metropolis, which in 2020 is estimated a population of 630,000. It has had a troubled history but is nowadays safe to visit and has the best-developed visitor facilities in Northern Ireland. And its situation means that Belfast can confidently claim to be the most fascinating city in both the United Kingdom and in Ireland.
This noble city is named for a mud bank and built upon sludge. The lower River Lagan is tidal and receives a dozen small tributaries (nowadays culverted) which drop their silt, forming banks of sand and mud. The lowest point at which you could ford the river at low tide is where the Lagan road bridge now crosses, and in Irish this is Béal Feirste, "river-mouth of the sand-bank ford". The tributary joining at that point, the Farset, is likewise named for the mud bank, not vice versa. And besides the man-made channels and culverts, a great volume of water seeps through the alluvial silt on both sides of the Lagan. It's a slimy, thixotropic impediment to building - clay dug out of a trench quickly feels homesick and slides back in - and a deterrent to high-rise; but Paris grew up on similar foundations.