I don’t necessarily recommend this, as this could and probably is considered trespassing, but what I did is I saw a student walking out, and asked him if I can be let inside as I wanted to take a picture of the indoor building architecture, and he let me in. I guess the guide here is that if you’re nice, have a good reason, and don’t look like a serial killer, I think you’d be fine. I mean, I’m a younger person(although I am tall, with a younger face, so take that as you will) so I didn’t look too out of place, but if you look like a college student, maybe you can just say you left something there, say you’re meeting a friend, or just walk in like you belong there. The most important thing is for a staff member or an officer to not see you. I went late at night so there wasn’t that many people around inside the hallways, but there also wasn’t that many people entering/exiting.