Am I being stupidly paranoid, or is this possible?

[polaris93]

Something just occurred to me concerning that Islamic cultural center that's supposed to open soon in New York City, two blocks from Ground Zero (on the 10th anniversary of 9-11, yet!): assuming you could get the materials and bring them in underground via a tunnel or something, what a great place a basement there would be to build a nuclear device intended to destroy the city above. You could detonate it remotely or from within the building (depending on whether you wanted to live to bomb again or become another Glorious Martyr to Islam, regardless of how many innocent lives, Muslim and otherwise, you took in the process).

Somebody please please please prove to my satisfaction that that is impossible!