Given that you'll arrive right down town at Union Station I suggest a brief walk over to the Sears Tower and take a trip up to the "SkyDeck". For a small fee you ride one of the fastest elevators in the world . . . yes, your ears WILL pop, and you can get a 360 degree of Chicago-Land. If you're lucky ORD
approach will be over the lake.
Once done there, perhaps a short trip out to see what's left of Meigs Field
Get hungry I highly recommend a good old fashioned Chicago Style Hot Dog, complete with pepeprs, pickles, tomatoes and celery salt. Want something different, then get a big, sloppy Italian Beef Sandwich. Geez, I'd love one of those right now! To blazes with those high speed restaurants - you can get the same steak in NO that you can get in Chi-Town, go for the local rations.
There are so many things to do in downtown Chi-Town, not knowing your likes/dislikes, it's hard to make a lot of recommendations.
FOR THOSE THAT FOUGHT FOR IT, FREEDOM HAS A FLAVOR THE PROTECTED WILL NEVER KNOW OR UNDERSTAND