FILE - In this June 1, 2006, file photo, the Tribune Tower, left, is reflected in a sheet of glass in Chicago. Tribune Media said, Thursday, Oct. 8, 2015, that it's hired a real estate investment banker to explore the sale of its Tribune Tower, its headquarters that sits on three acres along Chicago's Michigan Avenue. (AP Photo/Nam Y. Huh, File)CHICAGO (AP) — A 36-story Chicago landmark, the Tribune Tower, is up for sale. Tribune Media Co. announced Thursday that it has hired real estate investment banking firm Eastdil Secured to explore a sale or find a partner to help redevelop the building, which is home to the Chicago Tribune. Tribune Media phrased the move as an exploration of “strategic monetization alternatives.” The building sits on 3 acres along Chicago’s Michigan Avenue. Here are some features of the historic edifice that make it significant: