September 11 Memorial Bell offered to New York by London, New York, United States of America, North America

Aerial view over Manhattan skyline, looking uptown from the World Trade Centre, pre 11 September 2001, New York City, United States of America, North America

World Trade Center prior to 11 September 2001, Manhattan, New York City, New York, United States of America, North America

Low angle view of the exterior of the World Trade Center Twin Towers (419m), destroyed 11 September 2001, Manhattan, New York City, New York, United States of America, North America

The World Trade Center's Twin Towers, 419m, prior to 11 September 2001, Manhattan, New York City, United States of America, North America

World Trade Center prior to 11 September 2001, Manhattan, New York City, New York, United States of America, North America

One of the two waterfalls at National September 11 Memorial, World Trade Center, Manhattan, New York City, New York, USA

One World Trade Center also known as Tower 1 and Freedom Tower, Manhattan, New York City, New York, USA

One World Trade Center also known as Tower 1 and Freedom Tower, Manhattan, New York City, New York, USA

One World Trade Center also known as Tower 1 and Freedom Tower, Tower 7 on right, Manhattan, New York City, New York, USA

Names of September 11 2001 victims, National September 11 Memorial, World Trade Center, Manhattan, New York City, New York, USA

One of the two waterfalls at National September 11 Memorial, World Trade Center, Manhattan, New York City, New York, USA

Names of September 11 2001 victims, National September 11 Memorial, World Trade Center, Manhattan, New York City, New York, USA