Just for what it's worth, the Sears Tower observation deck doesn't have a glass floor, but there is a protrusion from the side of it, barely large enough for multiple people to stand in it, that does have glass walls and floors. It's relatively new.

If you come to Chicago, you should do the Sears Tower thing; it's not disappointing. I find the building disconcerting. On the upper floors, when there's a lot of wind, you can feel the building sway.

If you want to see uncryptic racism, you can go to the top of the Sears Tower and look west or south.