Reason No. 1 to not go to the Willis Tower... the glass on the 103rd floor just cracked under the feet of a mother and her two children. For real.
The protective layer of glass that supports the ledge cut out from the Willis Tower was what cracked but scared many that were standing near. If you haven't been to the Willis Tower you can step out onto a glass ledge that allows you to stand 103 stories up in the air being held by nothing but a piece of glass.
Well, that glass got tired and needed a break.