Panel discussions in conference rooms, libraries, coworking offices, and other spaces have their advantages. But when you are trying to accommodate an audience of hundreds of people there's no better setting than a stage. Stages offer more space for the panel participants as well as room for supporting technology like projectors, screens, accessory lighting, and audio-visual equipment.
Fortunately, Chicago has no shortage of suitable stages, most of which are set in auditorium spaces. Many are historic venues as well, whose prestige and success rate of holding important events will elevate the importance of your conference in the minds of attendees. The Auditorium Theatre, Art Institute of Chicago, and many local museums offer space for
private events, including large panel discussions.
These spaces are also renowned for the acoustics of the stage and auditorium. Good acoustics means less technology is required to enhance it. Not to mention a better experience for your audience and better video recordings to revisit.