...or maybe not so PD.
Visited the Pentagon, finally. A notice read (not verbatim): "Visitors are not allowed to converse in any other language but English in the course of the tour. No translations are allowed, either."
An Egyptian school-mate asked the unaware tour-guide if Arabs are allowed in. He thought over that, but fortunately concluded that he thought they should be...
All that after almost an hour of security checks.
*Tours are open to non-U.S. citizens, but have to be reserved in advance, just like any other. If the foreigners are joining a group, American nationals should be the ones making the reservation; otherwise, should be done through their embassy.