<p>I realize I’m a day late to this post, but if you are in the area in the future prior to matriculating, or anyone else that comes across this, you can use this advice.</p>
<p>Actually everything @mrduckyfeet said is impossible without special request for access, which I’ve never done but are usually difficult to get (I believe the only one you can get as a visitor is Butler access, which is actually definitely worth the effort. You can get it at Butler on the room to the left as you walk in). However, what you should know is that the buildings where classes take place are open usually from 9am-9pm every day, requires no special access, and classes are in session essentially five days a week all year. You should google: “columbia college bulletin”, search for a class you’re interested in, and find the classroom and time that it takes place. If you can’t find it there, try “columbia college directory of classes”. It has a much worse GUI but usually is more accurate. I would recommend doing this only for a class size that is over 50. Go to an introductory-level lecture for a topic you are interested in studying where you can sit in, understand what the professor is talking about, and not turn heads, so you can leave whenever you want.</p>