A little over 13 years after the September 11 terrorist attacks destroyed New York City's twin towers, the new World Trade Center is re-opened for business.

The 104-story One World Trade Center building stands as not only a reminder of the attacks themselves, but also as a technological breakthrough in architecture.

T.J. Gottesdiener of the Skidmore, Owings & Merrill firm that created the final design told The Associated Press that the tower was built with steel-reinforced concrete that makes it as terror attack-proof as possible and the firm went beyond the city's existing building codes to achieve that.

The iconic 1,776-foot tower is now the tallest building in America once again. "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 16-acre World Trade Center site.

Foye went on to describe the building as setting "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."

Publishing company Conde Nast is officially the first tenant of the new building as nearly 170 of its 3,400 employees are moving their offices in now. The company fills five floors in what Conde Nast CEO Chuck Townsend calls "the most secure office building in America."

One World Trade Center is currently 60 percent leased with another 80,000 square feet reserved for various businesses, including the advertising firm Kids Creative, the stadium operator Legends Hospitality, the BMB Group investment adviser, and executive office provider Servcorp.

The U.S. goverment's General Service Administration is on board for another 275,000 square feet while the cultural facility The China Center signed up for another 191,000 square feet.

The tower took eight years and $3.9 billion to build after the site suffered several years of political, financial, and legal battles. With 4 World Trade Center already built, and 3 World Trade Center nearing completion, the once devastated area is enjoying a rebirth of 60,000 residents, which is three times more than before September 11, 2001.

The original site was destroyed after two passenger jets were flown into the North and South towers of the original World Trade Center during terrorist attacks on September 11, 2001, leaving almost 3,000 people dead. Cleanup of the Lower Manhattan neighborhood finished in May of 2002 and the new tower broke ground on November 16, 2006.