So one of the aspects of Chicago that just blew me away was the history of Chicago and how it has been built up vertically 3 levels over time (lol read this link about the Chicago flood).
Even more amazing was the story about reversing the river flow. As most people know Chicago is on Lake Michigan. There is a river through the middle of town called the Chicago River.
Now what i didn't know is that the Chicago River used to flow east into Lake Michigan but because of the lack of water flow within the lake it used to poison and make sick the people of Chicago because this was also their fresh water supply.
So what they did was dig a canal some 26 miles to the south west to connect it into another river system - actually taking out more soil than the Suez canal.
This actually changed the direct of the river flow from heading east into Lake Michigan to heading west (technically it could actually drain Lake Michigan except for the introduction of 21 locks along the way).
It blew me away that you could get into a boat in Chicago and sail/float all the way eventually south west eventually coming out the Mississippi river in New Orleans via St Louis and Memphis along the way (sounds like an adventure that has to be done).