During the groundbreaking ceremony on April 6, 1970, a helicopter hovered 1,136 feet (346 m) over the site to demonstrate how tall the building would be.
Until the Shanghai World Financial Center was topped out in 2007, this was the tallest building in the world without any major antennae, spires, or finials at the top. In July 2009 a small communications antenna was installed on the roof.
From 1990 to 1992 the building's 43,000 marble cladding panels were replaced by two-inch-thick Mt. Airy granite panels at a cost of about $80 million.
Marble removed from the cladding of the building was crushed and used as decorative stone surrounding the Amoco refinery in Whiting, Indiana. The project was referred to as the "Whiting Beautification Project".
This was the tallest building in Chicago from 1973 until 1974, when it was surpassed by the Willis Tower.
The Standard Oil Company built this tower to replace its old headquarters on South Michigan Avenue, now known as the Michigan Avenue Lofts.
A "Sounding Sculpture" by Harry Bertoia is split between the east and west plazas. Its metal rods make soft music in the wind. The sculpture was originally a single ensemble in front of the building.
Each side of the building has 15 vertical bands of black windows, recessed between triangular white piers.
Until 2009 this was the tallest building in the United States ever to change its name. It was originally called the Standard Oil Building (nicknamed "Big Stan"), and later the Amoco Building.
A sunken plaza leads to the main entrance off . Before a postmodernization in the 1990's the plaza was a secluded space with two groves of locust trees flanking a reflecting pool with the Bertoia sculpture.
Aon Center is the only regular "box-shaped" building in the world over 300 meters tall.
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