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The World Trade Center's original twin towers stood for almost 30 years and cost $400m to build.

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Architect Daniel Libeskind won the competition to design their replacement.

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But concerns about a lack office space forced a redesign.

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Architect David Childs made the modifications to Libeskind's design.

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Despite disagreements over the designs, there was a show of unity when the final model was unveiled.

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The new building will dominate the New York skyline by day...

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...and by night.

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But at the site of the destroyed towers, a new building seems a long way off.