Media playback is unsupported on your device Media caption One World Trade Center dominates the Manhattan skyline

More than 13 years after the original towers were destroyed in the 9/11 attacks, New York's World Trade Center has re-opened for business.

Employees at publishing giant Conde Nast are starting to move into the 104-storey One World Trade Center.

The $3.8bn (£2.4bn) skyscraper took eight years to build and is now the tallest building in the US.

It is 60% leased and the government's General Services Administration has signed up for 275,000 square feet.

"The New York City skyline is whole again," Patrick Foye, executive director of the Port Authority, which owns the restored site, said in a statement.

The 1,776ft (541m) tall skyscraper is at the centre of the site, which includes a memorial in the footprints of the old towers and a museum, opened this year.

An observation deck at the top of the building will eventually be open to the public.

Image copyright AP Image caption One World Trade Center now dominates the Manhattan skyline

Image copyright Reuters Image caption Some of the best views of the building are in New Jersey

Image copyright AP Image caption People gathered in the lobby

Mr Foye added the building was "the most secure office building in America".

TJ Gottesdiener of the Skidmore, Owings & Merrill firm that produced the final design said the high-rise went beyond the city's existing building code, and was built with steel-reinforced concrete.

About 170 of Conde Nast's employees will be moving into the building this week, filling five floors. About 3,000 more employees will join them in early 2015.

Space has also been leased to the advertising firm Kids Creative, the GSA, and 191,000 sq ft for the China Center, a trade and cultural space.

The new World Trade Center is the centrepiece of the 16-acre site where the twin towers once stood, before they came crashing down, killing more than 2,700 people.

Image copyright AP Image caption For many New Yorkers walking past, it was another Monday morning