In the thirteen years since the September 11 attack on the World Trade Center, Lower Manhattan and the New York City skyline have undergone a remarkable transformation.
Five years after terrorists destroyed the iconic Twin Towers, developers began construction on One World Trade Center, the 104-story tower that is now the tallest building in the United States. The tower, which stands in the northwest corner of what was known as Ground Zero, officially opened this year.
Below, watch just how much the skyline has changed over the years.
World Trade Center in 1971, Ground Zero in Oct. 2001, Freedom Tower in 2014. (Photos by Getty Images/Corbis)