On Wednesday, the company informed employees that it is close to reaching a deal with the Port Authority of New York and New Jersey to lease 1 million square feet of space inside One World Trade Center, the 1,776-foot-high skyscraper being built adjacent to ground zero, the site of the 9/11 attacks. Condé Nast will pay an estimated $2 billion over 25 years to become the anchor tenant of the building, which will become New York’s tallest upon completion.

“Through unprecedented collaborations with technology and energy leaders throughout the world, One World Trade Center’s design team used the latest methods to maximize efficiency, minimize waste and pollution, conserve water, improve air quality and reduce the impacts of the development,” according to the Port Authority.

The news was greeted with a broadly positive response. (It’s not every day that you see such diverse — and tough — critics as the New York Post’s Steve Cuozzo and Reuters’ Felix Salmon so roundly upbeat about a city development.)

The truth is, Condé Nast’s decision move its headquarters — and 5,000 employees — downtown, is an immense boost for lower Manhattan, and a crucial vote of confidence that will likely spur other companies to relocate there as well. The New York Times first reported news of Condé’s imminent pact, which had been brewing for several months. Steel construction on One World Trade Center has now exceeded the 64th floor, according to the Port Authority, and the building-in-progress can be seen as far away as New Jersey and Brooklyn.

Among the construction stats: 2.6 million square feet of office space on 104 floors; 45 thousand tons of steel; 200 thousand cubic yards of concrete; and 1 million square feet of glass. Oh, and 70 elevators. The current plan calls for Condé Nast to occupy approximately 20 of the lower floors (pictured above) beginning in 2013.

Naturally, given One World Trade Center’s location, safety and security are paramount concerns, and the Skidmore, Owings and Merrill design — over a decade in the making — went through several changes to satisfy public safety officials. In fact, One World Trade Center will be but one component of a comprehensive security environment in lower Manhattan, which will include the National September 11 Memorial & Museum and the World Trade Center Memorial, as well as several other office towers.

The Port Authority says the building is designed around a “strong, redundant steel moment frame” paired with a “concrete-core shear wall,” and “incorporates highly advanced state-of-the-art life-safety systems that exceed the requirements of the New York City Building Code and that will lead the way in developing new high-rise building standards.”

In addition, the Port Authority says the building will take advantage of “next generation of innovative energy sources, such as cogeneration and fuel cells, as well as off-site renewable wind and hydro power.”

And of course, One World Trade Center, also known as the Freedom Tower, will feature a giant communications antenna extending the New York City skyline to 1,776 feet.

How green will the new World Trade Center complex be? Consider this, from the latest World Trade Center fact sheet (see below): “The weight of the trees to be used in the plaza to complement the Memorial and Museum bring an equivalent total weight equal to about 30 times the weight of the Statue of Liberty.”

In a statement, Condé Nast CFO John Bellando said the company is “proud to take part in the ongoing renaissance of Lower Manhattan.”