The twin towers of the World Trade Center are going to be replaced by a memorial and five new towers.
All the rubble has been cleared from the site and the location has since been called Ground Zero.
The memorial
The two 'footprints' that mark the place where the WTC towers stood are going to become a memorial called Reflecting Absence.
There will be two pools of water that reflect the light and the spaces around these will be planted with trees and engraved with the names of the 2,900 people who died in the attacks.
The new towers
The highest of the new towers is going to be called the Freedom Tower. It will be the tallest building in the US at 1,776 feet (540m).
The four other towers will form a semi-circle around the memorial in the centre. Two of Britain's top architects, Lord Foster and Lord Rogers, are working on the designs.
Building work has started and it should be completed in 2012.