The One World Trade Centre - or Freedom Tower as it's become known - will today become the tallest building in New York.
Workers are set to erect steel columns that will make the structure over 1,250 feet high - just enough to pip the roof of the observation deck on the Empire State Building, according to the Daily Mail.
The building also still has four more floors to finish, at which point it will then become the tallest building in America, and the third tallest in the world.
Although this claim is a contentious one, as some critics suggest the 408ft needle that will sit on the roof should not be counted towards its official height, which will be 1,776 feet including it.
The Freedom Tower is being built on the site where the ill-fated Twin Towers once stood.
The building is a testament to the strength of the people in New York and is in honour of the 3,000 people who were killed when two planed hijacked by terrorists crashed into the buildings, causing them to collapse on 11 September 2001.
When it is complete, the Freedom Tower will stand at 1,776 feet. It will be home to offices, as well as housing the 9/11 Memorial Plaza, which opened to the public in September 2011 to commemorate the 10-year anniversary of the attacks.
Currently, the top five tallest buildings in the world are:
1 The Burj Khalifa in Dubai at 2,716 feet
2 Taipei 101 in Taipei, Taiwan, at 1,670 feet
3 Shanghai World Financial Centre, Shanghai, China, at 1,614 feet
4 International Commerce Centre in Hong Kong, China, 1,588 feet
5 Petronas Towers in Kuala Lumpur, Malaysia, 1,483 feet
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