This is the 19-story landmarked brick-and-concrete Modernist marvel, Manhattan's Starrett-Lehigh Building.
This shot was taken near the Frying Pan bar on the Hudson River.
According to Wikipedia: In the 19th century, New York City required that all buildings higher than six stories be equipped with a rooftop water tower. This was necessary to prevent the need for excessively high pressures at lower elevations, which could burst pipes. In modern times, the towers have become fashionable in some circles.