Long before it became an archaic and filthy symbol of everything wrong with America’s broken cities, the New York subway was a marvel.In recent years, it has been falling apart.Today on The Sunday Read, a look at why failing to fix it would be a collective and historic act of self-destruction. This story was written by Jonathan Mahler and recorded by Audm. To hear more audio stories from publishers like The New York Times, download Audm for iPhone or Android.