The reconstructed World Trade Center welcomed its first tenant on Monday.

One World Trade Center is now the home of Condé Nast, a mass media company and a subsidiary of Advance Publications.

The 104-story building is the largest in the country, and will house many other multinational corporations. About 170 employees moved in on Monday, and 3,000 more Condé Nast workers are expected next year. The publishing giant's offices will occupy five floors.

"The New York City skyline is whole again, as One World Trade Center takes its place in Lower Manhattan," the Port Authority of New York and New Jersey Executive Director Patrick Foye said. The Port Authority owns the World Trade Center building and the 16 acres it sits on. The Twin Towers once stood on the site, and were destroyed in the 9/11 attacks.

The $3.9 billion skyscraper "sets new standards of design, construction, prestige and sustainability," Foye continued. "The opening of this iconic building is a major milestone in the transformation of Lower Manhattan into a thriving 24/7 neighbourhood."

The new World Trade Center complex also includes the National September 11 Memorial & Museum, The World Trade Center Transportation Hub, a performing arts center, retail space, and four other skyscrapers (Two, Three, Four, and Five World Trade Center).

Condé Nast CEO Chuck Townsend called One World Trade Center the "most secure office building in America."

Other occupants will include advertising firm Kids Creative, stadium operator Legends Hospitality, advisory and asset management firm BMB Group, and executive office provider Servcorp. About 60 per cent of the massive building is leased.

Condé Nast is known for its global magazine brands, including GQ, Allure, Glamour, Vogue, The New Yorker, Vanity Fair, W, and Wired. The company also owns social network and news site Reddit.