Belfast St Anne's Cathedral
Unlike the chief churches of other European cities, St Anne's Cathedral (often just called Belfast Cathedral) doesn't have a history stretching back far into the Renaissance or Middle Ages. It was begun in 1899 and, although basically finished in the 1980s, still lacks some finishing touches (like a steeple!)
Outside, it's a looming pile of stone, basically neo-Romanesque in style. Inside, it's intricately patterned, with black-and-white marble floors representing the paths of virtue and vice; immense stained glass windows; carvings depicting Belfast life; and a wondrous mosaic, made by two sisters out of countless pieces of colored glass.