The National September 11 Memorial and Museum, top, stands next to one of the reflecting pools on September 11, 2013, the 12th anniversary of the 2001 terrorist attacks.
Ground Zero now —
The National September 11 Memorial and Museum, top, stands next to one of the reflecting pools on September 11, 2013, the 12th anniversary of the 2001 terrorist attacks.
Mark Lennihan/AP
Pedestrians walk by One World Trade Center on the eve of the 11th anniversary of the September 11 terrorist attacks on September 10, 2012, in New York City.
Ground zero now —
Pedestrians walk by One World Trade Center on the eve of the 11th anniversary of the September 11 terrorist attacks on September 10, 2012, in New York City.
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A flag sits in a name on the 9/11 Memorial on September 11, 2012, before ceremonies marking the 11th anniversary of the terrorist attacks begin.
Ground zero now —
A flag sits in a name on the 9/11 Memorial on September 11, 2012, before ceremonies marking the 11th anniversary of the terrorist attacks begin.
Getty Images
The skyline of Lower Manhattan now contains One World Trade Center, which is scheduled to be completed in 2013.
Ground zero now —
The skyline of Lower Manhattan now contains One World Trade Center, which is scheduled to be completed in 2013.
Getty Images
New York's "Tribute in Light" for the victims of the 9/11 terrorist attacks shines into the sky over Manhattan on September 10, 2012.
Ground zero now —
New York's "Tribute in Light" for the victims of the 9/11 terrorist attacks shines into the sky over Manhattan on September 10, 2012.
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One World Trade Center is viewed from the 72nd floor of Four World Trade Center on Friday, September 7, 2012.
Ground zero now —
One World Trade Center is viewed from the 72nd floor of Four World Trade Center on Friday, September 7, 2012.
CNN
A view of One World Trade Center from the 72nd floor of Four World Trade Center on Friday.
Ground zero now —
A view of One World Trade Center from the 72nd floor of Four World Trade Center on Friday.
CNN
Construction workers continue to work on one of the four office towers being built on the site on Friday.
Ground zero now —
Construction workers continue to work on one of the four office towers being built on the site on Friday.
CNN
The progress of the construction on One World Trade Center can be seen in this photo, as well as one of the pools of the memorial site below.
Ground zero now —
The progress of the construction on One World Trade Center can be seen in this photo, as well as one of the pools of the memorial site below.
CNN
Construction workers work on the 72nd floor at Four World Trade Center on Friday.
Ground zero now —
Construction workers work on the 72nd floor at Four World Trade Center on Friday.
Getty Images
Visitors view the National September 11 Memorial & Museum on Friday. The memorial was completed in time for the 10th anniversary in 2011.
Ground zero now —
Visitors view the National September 11 Memorial & Museum on Friday. The memorial was completed in time for the 10th anniversary in 2011.
CNN
Only two of the four planned office towers for the site have had finishing beams placed on their top floors.
Ground zero now —
Only two of the four planned office towers for the site have had finishing beams placed on their top floors.
CNN
New York City is seen through a window of Four World Trade Center on Friday.
Ground zero now —
New York City is seen through a window of Four World Trade Center on Friday.
CNN
The reflecting pool at the National September 11 Memorial & Museum is viewed on Friday.
Ground zero now —
The reflecting pool at the National September 11 Memorial & Museum is viewed on Friday.
CNN
Visitors walk through the grounds of the National September 11 Memorial & Museum on Friday.
Ground zero now —
Visitors walk through the grounds of the National September 11 Memorial & Museum on Friday.
CNN