I'm sorry if my post is kinda off-topic, but something about the Twin Towers is for me a mystery:
You noticed that each of the twin towers had two black "lobby floors" at the trirds of the height.
The strange thing is that, depending were you were in NY, when you looked at the towers , some times you could see these "black lobby floors", some times you COULDN'T.
on this picture it's almost impossible to see:
And, on this picture, they are clearly seen:
Very strange, no ?
Was it the purpose of the architect ?