Holy cow !
Does everyone else see the "spelling is important" written across the top of the walls ?
I was just fooling around with different guesses, and when I came back to hall1 I found the above text scrawled on the walls, and I could've sworn they weren't there before !
Edit : Okay, I'm not sure how it happened but I've got it...I'm in hall 2 now. The hint is in what I wrote above.