TWIN TOWERS REDUX: A sinuous pair of double towers forms the centerpiece of Hadid's design -- the thinner for residential apartments, the wider for offices.

Showing a defiant confidence in Manhattan and in the very tall building, Zaha Hadid proposes a skyscraper that is higher, bigger, and more complex than the original World Trade Center towers. The London architect, noted for inventing forms that encourage social interaction in and around a building, evokes the original towers with a double set of sinuous twins, the thinner pair for residential use and the thicker for offices. But the new buildings are no longer extruded from square footprints like tubes. The four towers bend and merge at various points, the floor levels swelling and receding along the vertical axis to accommodate different uses. Hadid and her associate, Patrick Schumacher, reinvent the skyscraper as a building type, operating on the principle of connecting rather than isolating floors and people, and varying spaces rather than repeating them identically. They create a mille-feuille landscape whose folded and layered topography, comprising spaces dedicated to shopping, transport, and culture, are interwoven with passages linking the development, as in a complex root system. In tribute both to the dead and to the World Trade Center, the architects cut deeply into the towers' footprints, creating hollow tubes that become haunting voids.

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