BUILDING BIG: Databank: John Hancock Center

Today, the John Hancock Center in Chicago, Illinois, is affectionately known as "Big John," but it was not always this way. Located on North Michigan Avenue along Chicago's "Magnificent Mile," the skyscraper was controversial from the start for its enormous bulk and dark metal exterior. Eventually, it was celebrated for its very brashness, and today it remains one of Chicago's best-loved icons.

Currently, the John Hancock Center is the twelfth tallest building in the world. But to keep such a tall building standing in the "Windy City," engineers had to make the enormous structure super stiff. How did they do it? The John Hancock Center is actually a super-tall steel tube. Steel columns and beams are concentrated in the skyscraper's perimeter, and five enormous diagonal braces on the exterior walls of the skyscraper give it extra strength in the wind. The skyscraper also rises from 40,000 square feet at the base to 18,000 square feet at the summit. This tapered design provides additional structural stability against wind forces.

In order to reach the whopping height of 1,127, engineers knew that the enormous 384-million-pound tower needed caissons to prevent it from sinking into the soft ground. Today, the John Hancock Center rests on several caissons that extend down to bedrock. One of the caissons actually reaches 191 feet below the ground -- the deepest ever sunk in Chicago!

Fast Facts:

The diagonals completely block the view from two windows on each floor. Ironically, a rental agent has transformed these "blocked" windows into something of a status symbol -- it actually costs more money to rent from these rooms!
In 1997, the John Hancock Center was remodeled, and half of the 94th floor's southern windows were replaced with screens. Tourists can visit the "Skywalk," as it is called, and breathe the outside air and hear the noise of the city below.
Offices occupy the lower floors of the 100-story skyscraper, and apartments are located on the upper floors of the building. Additional facilities include restaurants, health clubs, a swimming pool, and even an ice-skating rink.