Getting a visitor's permit is (or maybe was — I don't know about the situation of last 2-3 years) relatively straightforward even for foreign tourists. That's in Russia, I don't know much about China.

Having grown up in relatively closed city of Omsk, Russia, I knew (like every other boy of my age) the exact coordinates of probable nuclear strikes in case of war (ICBM silos perimeter, tank production plant officialy known as transport machinery plant, nuclear weapons maintenance plants etc.) All of which were supposedly secret, but everyone knew everything anyway.