Inside the John Hancock building is a self-contained ice rink.

The large “X” shapes on the outside of the Hancock Building block certain windows entirely. These offices are more expensive than rooms where the views are not obstructed.

At the Sears Tower , six roof-mounted robotic window washing machines clean all 16,100 windows.

The average sway of the Sears Tower is approximately six inches (152 millimeters) from true center.

On top of the Sears Tower “days” are, on average, three minutes longer. It is the first place in Chicago the sun hits at sunrise .

After five years of widespread death – thanks to cholera and dysentery – killing more than six percent of the population a year, Chicago raised the street level more than seven feet so new sewers could be laid in 1856.

Lying just a few miles to the west of Lake Michigan 's shore is a natural subcontinental drainage divide which runs roughly along the path of what is now Harlem Avenue . This divide and the Chicago river created a swamp, on top of which the entire city is built.

The address of your home means more then you think . Even numbers indicate a building on the north or west side of a street, while odd numbers mean a location on the south or the east side of a street.

The Home Insurance Building, standing at the northeast corner of LaSalle and Adams streets – on the site now occupied by the west portion of the Marshall Fields building – was the world's first skyscraper, built in 1885. .

Built with money donated by Kate Buckingham as a tribute to her brother, the Buckingham Fountain is the second-largest fountain in the world.

The city's lakefront has more than 15 miles of bathing beaches, which is more then half of Chicago's total lakefront .

The city also boasts the world's largest bakery , owned by Nabisco and located at 7300 South Kedzie Avenue .

The Merchandise Mart is the world's largest commercial office building.

The world's largest public library is the Harold Washington Library Center .

The world's longest street is Western Avenue .

Erected in 1946, the Wrigley Building was the world's first air-conditioned office building.

The Shedd Aquarium is the largest indoor aquarium in the world.