All ready: Water flows in the fountains of the National September 11 Memorial in New York on Saturday, ahead of the 10th anniversary of 9/11

Remembered: Former U.S. presidents George W. Bush, left, and Bill Clinton, right, and former first lady Laura Bush, centre, bow their heads during ceremonies marking the 10th anniversary of the 9/11 attack in Shanksville, Pennsylvania, on Saturday

Into the sky: The 'Tribute in Light' shines above lower Manhattan, the Statue of Liberty, and One World Trade Center, left, on Saturday in New York

Service: Flags are carried into St. Patrick's Cathedral during a memorial ceremony on Saturday to honor New York firefighters that were killed in the attacks on the World Trade Center

(St Patrick’s Cathedral)

Linking arms: To commemorate the 10 year anniversary of the September 11 attacks, people participate in the 'Hand-In-Hand 9/11' ceremony by holding hands for a moment of silence at 8:46am, the time that the north tower of the World Trade Center was hit

Empty Sky Memorial structure is seen during the structure's dedication at Liberty State Park

First glimpse: Aeriel view of Ground Zero taken from Washington Street the day before the official 9/11 memorial service