Reference

The Crain Communications Building in Chicago is often referred to as the "Diamond Building" due to its distinctive architectural feature. The top of the building has a unique diamond-shaped facade, which makes it easily recognizable on the Chicago skyline. The diamond shape is not only a significant design element but also contributes to the building's nickname.

Here's a visual reference to its diamond-shaped top:

For additional details, you can refer to the Simple English Wikipedia page on the Crain Communications Building.