A five-minute primer on an issue making headlines
Work has finally started on New York's Freedom Tower, the skyscraper that will rise from the site of the World Trade Centre. It has been almost five years since the 9/11 terrorist attacks. How long will the work take?
The Freedom Tower is scheduled to be finished by 2012 but it has been a fraught process getting to this stage, with repeated disputes over redeveloping Ground Zero. Until last month the site's landlord, developer Larry Silverstein, and its owner, the city's Port Authority, were at loggerheads. But a deal has been done and Mr Silverstein will build four of the five skyscrapers on the site. On completion, he will hand over the Freedom Tower and another building to the authority.
The Freedom Tower's design has changed several times. What does this blueprint look like?
It will be among the world's tallest buildings at 82 storeys - the same number as the Twin Towers destroyed in 2001. With its decorative spire it will reach 540 metres, or 1,776 feet, a figure that matches the year of American independence. It was initially envisaged that the building would encompass a swirling design evocative of the Statue of Liberty, but police said it would be vulnerable to truck bombs similar to one used to attack the Twin Towers in 1993. The new building will have a 60-metre blast-resistant base coated in titanium to withstand any repeats.
How much support is there for replicating the height of the Twin Towers?