Barbara L. Nelson is editor of Real Estate New York.

NEW YORK CITY-Four days before the fifth anniversary of the Sept. 11 terrorist attacks, conceptual designs were unveiled for World Trade Center Towers 2, 3 and 4 yesterday by three world-renowned architects, completing Larry Silverstein and Daniel Libeskind's vision for Ground Zero.

The three towers respectively were designed by architects Lord Norman Foster, Lord Richard Rogers both of England and Fumihiko Maki of Japan, bringing the total number of architects associated with Ground Zero to seven. Libeskind with his master plan, David Childs the designer of the Freedom Tower, and Santiago Calatrava, the architect for the World Trade Center transit hub, round out the elite group.

Gov. George Pataki gave Silverstein, president of Silverstein Properties, until Sept. 7 to come up with designs for the three towers Silverstein is committed to building by 2012, according to an agreement reached with the Port Authority last April.