Chicago is home to one of the tallest buildings in the world: the Willis Tower. So tall that on a windy day, the topmost floors can sway as much as three feet. But what keeps it from falling?

including at a new restaurant inside the CNA building at 151 N. Franklin St. in late October and the expanded Willis Tower location, which debuted its robotic salad assembly line Monday.

Willis Tower and its Skydeck sit above South Wacker Drive on the western edge of the Loop. You'll find the Quincy/Wells L station nearby, as well as several bus stops and a parking garage.

Landmark opened in 1973 with original tenant Sears Roebuck & Co. CHICAGO, Illinois (CNN) -- Sears Tower is history. As of Thursday, the iconic Chicago, Illinois, skyscraper is now named Willis Tower.

Chicago is home to one of the tallest buildings in the world: the Willis Tower. So tall that on a windy day, the topmost floors can sway as much as three feet. But what keeps it from falling?