Aon Center

The third tallest building in Chicago was originally known as the Standard Oil Building and later the Amoco Building. At 83 floors, it was the tallest in the city and the fourth tallest in the world upon completion—until the Sears Tower (now Willis Tower) opened a year later. The exterior was originally clad in thin slabs of Carrara marble that proved to be unfit for winter weather. As a result, a massive project to re-clad the entire building in granite took place from 1990 to 1992.

Edward Durell Stone, 1972