What is there to do that the Sears Tower(Willis Tower)in Chicago?

You basically just look at the view. It's pretty cool actually, as long as it's a clear day/night. If it's kinda cloudy or foggy though, you probably won't be able to see very far, so it's not really worth going up then. If you don't think it sounds very interesting, you don't have to go. There are plenty of other things to do in Chicago.