Learn about the development of “intelligent concrete”—the strongest concrete ever made—in this clip from Super Skyscrapers focusing on the construction of 1 World Trade Center in New York City. In response to the tragedy of 9/11, the architects and planners of 1 World Trade Center developed new techniques for creating extra-safe buildings, such as “intelligent concrete,” which can withstand pressure four times that of traditional concrete. This concrete provides the material for each floor as well as the core of the building. This clip follows the WTC’s concrete workers as they supervise the pumping of the concrete up to the 102nd floor.