I wonder if he just chose these as the biggest, most popular or do they have a meaning? Most of the London bombing stations like King George could have had a second meaning.
I can't find a second meaning.
I think in this case, it's "Manhattan" for the sake of it being Manhattan as mentioned in bin Laden's speeches and his obsession with New York in general.
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The following are excerpts from Osama bin Laden's speech on the eve of the 2004 US elections:
Osama bin Laden: Oh the American people, I address these words to you regarding the optimal manner of avoiding another Manhattan, and regarding the war, its causes and its consequences. But before this, I say to you: Security is one of the important pillars of human life, and free men do not take their security lightly, contrary to Bush's claim that we hate freedom. Let him explain why we did not attack Sweden, for example. Clearly, those who hate freedom have no pride, unlike the 19, may Allah have mercy on them. We have been fighting you because we are free men who do not remain silent in the face of injustice. We want to restore our [Islamic] nation's freedom. Just as you violate our security, we violate yours. (snip)
http://www.memritv.org/Transcript.asp?P1=312
Is there a Columbus day parade in NY?
I think they have one in Chicago, if I recall correctly.