The first new office tower at New York City's Ground Zero opened on Wednesday, marking a rebirth of the Lower Manhattan site where old World Trade Center towers were destroyed in the Sept. 11, 2001, terrorist attacks. The 72-story 4 World Trade Center becomes the first skyscraper that opens its revolving doors for business on the original 16- acre site where about 2,700 people were killed when hijacked airplanes crashed into the World Trade Center twin towers. "Four World Trade is the first building to be completed within the borders of the original World Trade Center, and is a testament to the strength and resiliency of New Yorkers," New York Mayor Michael Bloomberg said at an outdoor ribbon-cutting ceremony for the glass building. "For New Yorkers, 4 World Trade Center is not just the next great building to grace our skyline. It's a symbol of our resiliency, and a testament to our will," Manhattan Borough President Scott M. Stringer said at the ceremony. "And this is just the start. Next year, One World Trade will follow, helping to continue the amazing revitalization of Lower Manhattan and its business community. This is a proud day for New York city," he said. Designed by Japanese Pritzker-Prize winning architect Fumihiko Maki, the 298-meter tower is the smallest among the four main buildings planned for the site. One World Trade Center, the crown jewel at the complex, will not be completed until early 2014. Rising 541 meters from the ashes of Ground Zero, it was designated the tallest skyscraper in the United States on Tuesday. So far, more than 40 percent of its 213,677-square-meter of office space of 4 World Trade Center remains unleased, according to Silverstein Properties, Inc., the developer of the building. The Port Authority and the Human Resources Administration for the City of New York are 4 World Trade Center's only two tenants for the time being, taking up nearly 60 percent of its new office space. Office workers are expected to move into the tower early next year.