The city of Chicago is truly a city of neighborhoods. However Downtown Chicago is like a concrete organism that living on all the people moving in and out of it's arteries and veins. Every time I go downtown I think of Nelson Algren:

"By nights when the yellow salamanders of the EL bend all one way and the cold rain runs with the red-lit rain.
By the way the city's million wires are burdened only by lightest snow;
When chairs are stacked and glasses are turned and arc-lamps all are dimmed.
By days when the wind bangs alley gates ajar and the sun goes by on the wind.
By nights when the moon is an only child above the measured thunder of the cars, you may know Chicago's heart at last."
Nelson Algren: Chicago: City on the Make

Nelson Algren Commitee
http://www.nelsonalgren.org/

Chicago Architecture Tours
http://www.architecture.org/