The Empire State Building

If you're ever in New York City, you must check out the Empire State Building.

And if you do go to the Empire State Building, be sure to go at night.  Not only are the views more spectacular at night (see photos below), the later you go, the less people there are.  Since New York has the reputation as "the city that never sleeps", it will come as no surprise that the observation deck at the Empire State Building is open until 2:00 am.  With less people, the lines are much shorter and you can enjoy the view much better with less people fighting for position on the observation deck.

This is the view to the south.

And this is the view to the north.  The area with the bright lights in the lower center of the picture is Times Square; another New York attraction best viewed at night.