An interesting late addition to the what-to-do-with-Ground-Zero proposals - build this amazing skyscraper as originally planned and designed for Manhattan by Gaudi:

...the hotel was to have been rainbow-hued in tile and marble. The hotel would have been a group of clustered towers, of reinforced concrete over steel, in Gaudi's sturdy trademark parabolic shapes

[...]

In the central tower there were to be five monumental dining rooms dedicated to five continents; each was to seat 400.

Yet another dining room on the sixth floor was to be topped by an exhibition hall, and above that was planned a theater and conference room.

Atop that was to be a cathedral-like 375-foot-high space honoring all the American presidents, in a hall decorated with stained glass windows, mosaics and frescos.

The starlike top, which Matamala said was called the sphere of all space, would have afforded a panoramic view...

Postmodern? In a Manner of Speaking [New York Times]