The tall building (311 South Wacker -- it's 'real' name) is my favorite in the city. It's nickname is the "wedding ring" building (or white castle). The top of the building is a replica (urban legend? fact?) of the engagement ring the architect gave his wife. The color of the 'diamond' changes depending on what is being honored. Of course, it's red this week!
Thanks all -- I appreciate your taking the time to comment.