Six hours?
Six hours is a long time to be at O'Hare. I'd take an EL downtown and hangout, maybe go up to the top of Sears Tower or Hancock building, I don't know...shop on Magnificent Mile, etc...
That should leave you plenty of time depending on the traffic, but I wouldn't cut it too close in gettin' back.
Have fun!
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[This message has been edited by CS (edited 11-06-2003).]