Nearly six million people have stepped out onto see-through ledges atop Chicago's tallest building to see the streetscape below and the surrounding metropolitan area.
The Willis Tower, formerly known as the Sears Tower, released that figure this week -- four years after the tourist attraction opened in 2009.
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The series of glass bays jut out from the 103rd floor of the building that's dominated Chicago's skyline for four decades.
The see-through floors are collectively known as The Ledge and they are in the longer-established Skydeck section of the skyscraper.
More than 1.5 million visitors stepped out onto The Ledge in 2012 alone.