Earlier quoted context omitted.
> that cannot be displayed to the public in fear of damaging them I saw the Mona Lisa at the Louvre on vacation. It was being displayed on a wall like any other painting but it had a big sign, saying no flash photography. There was a large crowd in front and there was a constant flashing from cameras. I wanted to yell at everyone but it wouldn't have done any good.
Was that the original? I remember seeing Lady with an Ermine in Poland - really thick glass in front, dark room, people reminding you about the flash before going in. And I imagine that's not even remotely as important painting.
Yes. It was 30 years ago so they have probably improved the protection since then.