Forty percent of Manhattan's buildings couldn't be built under the present New York zoning code. Under current zoning regulations these buildings would not get planning permission because they are either too tall, have too many apartments or too many businesses.
The New York Times has created an interactive map showing Which Buildings Couldn't be Built in Manhattan Today. The footprints of the buildings which would fall foul of the current zoning code are colored on the map. You can find out which particular codes they would break by using the filters in the map sidebar.
This article also includes static maps of the same data used in the interactive maps. These static maps highlight Manhattan buildings which would fail to meet New York's zoning codes for height, the number of apartments and the number of commercial businesses.