Torquere

Now known as 875 North Michigan Avenue—yuck—this will always be the Hancock Building to me. From the Wiki:

[It] is a 100-story, 1,128-foot-tall (344-meter)[7] supertall skyscraper located in Chicago, Illinois. Located in the Magnificent Mile district, the building was designed by Peruvian-American chief designer Bruce Graham and Bangladeshi-American structural engineer Fazlur Rahman Khan of Skidmore, Owings and Merrill (SOM).[8] When the building topped out on May 6, 1968,[1] it was the second-tallest building in the world after the Empire State Building, in New York City, and the tallest in Chicago. It is currently the fifth-tallest building in Chicago and the fourteenth-tallest in the United States, behind the Aon Center in Chicago and ahead of the Comcast Technology Center in Philadelphia. When measured to the top of its antenna masts, it stands at 1,500 feet (457 m).

One of the most famous buildings of the structural expressionist style, the skyscraper's distinctive X-braced exterior shows that the structure's skin is part of its "tubular system". This is one of the engineering techniques which the designers used to achieve a record height; the tubular system is the structure that keeps the building upright during wind and earthquake loads. This X-bracing allows for both higher performance from tall structures and the ability to open up the inside floorplan. Such original features have allowed 875 North Michigan Avenue to become an architectural icon. It was pioneered by Bangladeshi-American structural civil engineer Fazlur Khan and chief architect Bruce Graham.

It's simply magnificent. The name of this piece is Torquere. The classical Latin verb torquere means to twist, turn, or wrench. Its later Vulgar Latin derivative *torsare (meaning to bind or pack, the source of the English word truss) stems directly from torsus, the altered past participle form of torquere.