What is the official height of Chicago’s Aon Center in metres?

Chicago’s Aon Center has an official architectural height of 346 metres.

Completed in 1973, the tower was designed by the architectural firm Edward Durell Stone & Associates. It rises 83 stories above Chicago’s Loop and is clad in white Carrara marble, an unusual material choice for a skyscraper of its scale. The building was originally known as the Standard Oil Building and was later called the Amoco Building before taking the Aon name.

The tower’s marble exterior became a major engineering concern. Sections of the cladding were removed and replaced with granite after marble panels cracked or shifted. This repair work changed the building’s appearance slightly while improving its long-term durability.

The Aon Center is often confused with Chicago’s taller Willis Tower or with the nearby Prudential Plaza buildings. Its 346-metre figure is the architectural height, measured to the top of the building rather than to a later communications antenna.