Rebuilding Ground Zero

The lower Manhattan skyline as proposed after the construction of the future Freedom Tower and other buildings. Developer Larry Silverstein and the architects Norman Foster, Richard Rogers and Fuhimo Maki unveiled designs for three new skyscrapers on the site of the former World Trade Centre Photograph: /Getty Images

An artist's rendering by Studio Daniel Libeskind shows the original plan for the proposed new World Trade Centre that was unveiled in 2003 Photograph: /EPA

The twins towers before the terrorist attacks on 11 September 2001 Photograph: /EPA

An aerial view looking north from southern Manhattan as smoke rises from the ruins of the World Trade Centre three days after the 9/11 attacks Photograph: EPA

An aerial view, taken on 23 September 2001, shows the remains of the twin towers Photograph: Gregg Brown/Getty

The then director of the Federal Emergency Management Agency, Joe Allbaugh, front right, looks over wreckage on 16 September 2001 Photograph: Reuters

Work continues on clearing the World Trade Centre site on 2 January 2002 Photograph: Mark Lennihan/AP

Debris and recovery removal work continues at Ground Zero on 25 March 2002 Photograph: Spencer Platt/Getty

An aerial view shows lower Manhattan and the World Trade Centre site on 31 May 2002 Photograph: Gregg Brown/Getty

Buildings in Manhattan's financial district stand tall over the empty site on 7 September 2002, almost a year after the attacks Photograph: Stephen Jaffe/EPA

Work continues at the World Trade Centre site on 17 July 2003 Photograph: Mario Tama/Getty

The World Trade Centre site as of 6 October 2004 Photograph: Spencer Platt/Getty

Four years on from 9/11, work continues at the site on 30 September 2005 Photograph: Stephen Chernin/Getty

An aerial view of Ground Zero on 11 May 2006 Photograph: Stan Honda/AFP

A model of the future World Trade Centre development sits in front of the Ground Zero construction site on 6 September 2007 Photograph: Emmanuel Dunand/AFP

Ground Zero on 4 September 2007 Photograph: Mario Tama/Getty

An aerial view of lower Manhattan on 29 August 2007 Photograph: Mark Lennihan/AP

Construction workers operate heavy machinery at Ground Zero on 6 September 2007 Photograph: Emmanuel Dunand/AFP

Workers continue to build the foundation of the Freedom Tower at the site on 4 September 2008 Photograph: Spencer Platt/Getty

The World Trade Centre site as of 8 September 2008 Photograph: Mark Lennihan/AP