Look, if they didn't want you to open this door, they wouldn't have put it in the wall here behind an intimidating moat and drawbridge. With great effort, you manage to push it open enough to squeeze through. Inside you find a large amount of people, all wearing disguises, moving about. No one's noticed you yet, and luckily you see some materials here you'll be able to use to construct a disguise you'll be able to use to move about unsuspiciously.