3Eleven, the 25-story apartment tower in River North from The John Buck Company, has reached the glass milestone. Not the glass ceiling, mind you. So far, only the windows are glass. As the tower rises to the 17th floor or so, Power Construction is starting to glaze up the exterior. 3Eleven will hold 245 rental units, 3,000 square feet of retail, and 109 parking spaces, some of which will be shared with Assumption Catholic Church next door.