New York's skyline whole again as One World Trade Centre opens for business

One hundred and four stories tall, and $4bn later, One World Trade Centre has been resurrected as America's answer to the September 11 attacks.

The first company to move in is the magazine publisher Conde Nast. First thing, 3500 workers for Vogue, GQ and Vanity Fair turned up for work.

Many worried about moving into a building which is a potential target for another terrorist attack. There have been months of meetings to reassure them.

"A lot of sad things happened here and this is a good start to get things going in the right direction," employee Peter Matthew said.

To prevent a collapse like back on 9/11, the tower was built with a massive super-strengthened concrete centre.

The elevators and fire escape stairways are all within that core, so people could get out from above and below any floor which might be burning.

It is the tallest skyscraper in America, although so far only 40 percent of the space has been leased.

"We give this building back to the people of New York as a gift. A gift of remembrance of people we lost that fateful day. But also of the wonder of how people pull together," said builder Steve Plait.

After 13 years, New York's skyline is whole again.