Construction workers gather inside the Oculus at the World Trade Center during the grand opening of Westfield's shopping complex on Tuesday in New York.

Westfield opened the 365,000 sq ft (34,000 sq m) complex mainly inside the Oculus, the white-ribbed centrepiece of architect Santiago Calatrava's US$3.9 billion (S$5.2 billion) commuter terminal.

The opening was the latest step in a return to normalcy at the trade centre, where there are two completed office towers and a third on the way, along with a 9/11 memorial and museum honouring the victims of the attack in 2001.

The trade centre's shopping hub will have the delicate task of co-existing with the solemn memorial, with its twin pools approximately where the destroyed twin towers were, reported Bloomberg.

For many victims' families, the memorial remains their only grave site. The complex is planned so stores can operate without intruding on the memorial as none of the entrances faces the memorial.

Westfield is expecting 15 million travellers to visit the area annually.