One57 does for Central Park what
One WTC does for Downtown, they both anchor their respective areas.
When
432 Park Ave is complete, that tower will join
One57 (almost like twin towers), where they both serve as anchors for Central Park -- so no matter where in the city you are (even if you are in NJ), all you need to do is look and you will instantly know where Central Park South begins.
These towers serve as a visual compass for the NY'er in all of us.