World Trade Center site, aerial photograph. The twin towers of the World Trade Center occupied the vacant area at upper left until they were destroyed in a terrorist attack on 11th September 2001. Two hijacked commercial aircraft were flown into the two main towers, causing them to collapse. This led to some 3000 deaths. A new building, called the Freedom Tower, is planned to be built on the site by 2009. At 1776 feet (1776 was the year of the US Declaration of Independence) it will be the tallest building in the world.