The Hearst Tower, designed by London architect Sir Norman Foster. The 46-story building just off Columbus Circle at 57th Street was built on top of the existing six-story headquarters of the Hearst publishing company.

With its diagonal grid, it is the first office tower in North America to be built without vertical steel beams. And according to the architects, the "diagrid" structure saves steel -- it uses 20% less than a typical building of its height. It was designed to be "green," too. Lights inside adjust according to the amount of natural light coming in and turn off when motion sensors detect no movement. The roof collects rainwater and uses it to water plants and replenish the A/C system's evaporated water. The Hearst Tower was certified as New York City's first green building with a Gold rating for Leadership in Energy and Environmental Design (LEED) by the U.S. Green Building Council a year ago this month.