Entrance to kohanim [Jewish priests] forbidden
I found this curious sign at the Haifa Educational Zoo, and I'm pretty sure that Israel is the only country in the world in whose zoos you will find warnings of this sort, aimed at preventing a violation of halakha, or Jewish law. Other than the usual caged animals, the Haifa Zoo also hosts little museums and exhibits (which look rather old-fashioned), at the entrance to one of which I stumbled upon this sign and observed an interesting scene.
A group of school children were invited into the room, but after reading the sign which forbids entrance to kohanim, i.e., descendants of priests in the Jewish Temple, some of the kids started shouting to the guide that their classmate wasn't allowed in since he was a kohen. The boy, who looked about 13, seemed confused. He didn't know whether to follow his classmates into the room or not, and kind of hung around the door. After having settled everyone else down, the guide looked at the poor kid who was the source of great disruption, and said, "You're either in or you're out!"
After darting in and out of the door a few more times, he finally decided to stay.
I think what confused him the most was that he wasn't really sure who was supposed to forbid him to enter the room: the zoo authorities (and hence the guide), he himself, G-d, or someone else.
When I peaked into the room, I understood why the sign had been posted. Most of the room's display consisted of stuffed, mounted animals such as birds and desert mammals. However, there was one old display case with human fetuses in formaldehyde, which obviously caused very strong reactions in the visitors.
Although the rules derived from the Torah are complex, in brief, dead bodies and body parts are considered ritually defiling and therefore kohanim are not allowed to be close to them.