It may be a cliche to say we're always discovering new things in New York. But have you ever heard of "Sixth-and-a-Half Avenue"? It's a string of public access corridors through huge private office towers that lead you from 57th Street to 51st.
According to our rigorous research in Wikipedia, they were created in 2011 to relieve pedestrian congestion. But now, they are criticized as having created vehicle congestion as cars slow down for people to cross the street between buildings. Can't win.