Thirteen years after the 9/11 terrorist attack, World Trade Center is opening for business again.

Conde Nast will start moving Monday into One World Trade Center, a 104-story, $3.9 billion skyscraper that dominates the Manhattan skyline.

It's the centerpiece of the 16-acre site where the decimated twin towers once stood and where more than 2,700 people died on Sept. 11, 2001, buried under smoking mounds of fiery debris.

"The New York City skyline is whole again, as One World Trade Center takes its place in Lower Manhattan," said Patrick Foye, executive director of the Port Authority of New York and New Jersey that owns both the building and the World Trade Center site.

He said One World Trade Center "sets new standards of design, construction, prestige and sustainability; the opening of this iconic building is a major milestone in the transformation of Lower Manhattan into a thriving 24/7 neighborhood."

With the construction fences gone, Americas tallest building is considered by Conde Nast CEO Chuck Townsend as the, most secure office building in America.

About 3,000 employees will join the 170 expected to move in Monday in 2015. The publishing giants will take over five floors of the building.

The building is 60 percent leased, with another 80,000 square feet going to the advertising firm Kids Creative, the stadium operator Legends Hospitality, the BMB Group investment adviser, and Servcorp, a provider of executive offices.

The tower overlooks the National September 11 Memorial and Museum. Its aim is to honor those who died in the terrorist attacks.

For years, the grisly pit where workers found mostly body parts was dubbed the "ground zero" of the aerial terror attack.

At night, the incandescent steel-and-glass behemoth can be seen from vessels in New York Harbor approaching Manhattan.

Soon, an observation deck will be open to the public.

The eight-year construction of the 1,776-foot high skyscraper came after years of political, financial and legal infighting that threatened to derail the project.

The bickering slowly died down as two other towers started going up on the southeast end of the site: the now completed 4 World Trade Center whose anchor tenant is the Port Authority, and 3 World Trade Center that's slowly rising.