On the outskirts of Varadero, a service station that I was told didn't have any gas.
We drove by a school that day that was "supposedly" a factory for making bullets according to a local. It was too risky to take a photo.
Some things in Cuba should not be photographed... military installations, army personnel, and police officers. They tell you to not even try. Although, some do seem to pose for you, but not happily like in some countries.
If you travel to Cuba as a serious photographer, with lots of lenses and equipment, you will surely get asked about it when you arrive. It's a good idea to be discreet. I've heard stories of people actually being followed on their trip, especially back when Fidel Castro was in power.
Also, some major tourist attractions have an "annoying" photo fee clearly stated at the entrance and you may find a museum guard following you around ready to ask for payment.
Photo: Canon EOS 650 AF SLR Film Camera (digitized print)