Now that the 601W Cos owns Aon Center free and clear, the group is ready to make its mark on Chicago's fourth-tallest skyscraper. The firm says an observatory atop the 83-story tower is in its long-range plans. If realized, this would make Chicago the second city in North America with observatories atop three supertalls.

An observation deck was touted as one of several value-adds to prospective buyers by Aon Center's former owner, Piedmont Office Realty Trust. 601 managing principal Mark Karasick believes the views offered at Aon Center are worth the investment. Karasick told Crain's the unobstructed views would complement the existing observation decks at Willis Tower and the John Hancock Center.

New ownership also plans on extending Aon Center's retail out from the building to the street, and wants to use the top two floors for some sort of restaurant and bar. [Crain's]