All of today's flourishing cities have notable public realms. Some, such as London, have public realms so vivid that a single image—say, of the Thames or Westminster—conveys the whole. Paris's boulevards, Chicago's lakefront, Philadelphia's City Hall, New York's Brooklyn Bridge announce their cities instantly.
Public spaces have unique symbolic power, which, of course, also makes them attractive to terrorists. But cities can't regenerate without vital public spaces.