Here's a photo (several, actually) that you're not allowed to take - of the ceiling of the Sistine Chapel.
I was standing there a few days ago (says he casually as a throw away line) admiring the ceiling which has been restored and is an amazing sight. In the crush of the mob loudspeakers kept warning me that photos and videos of the ceiling are not allowed. They also instructed us that absolute silence was required, a rather contrary amplified command that ironically made more noise than the assembled masses they were trying to silence!
Now I've been here before, and was greatly disappointed on that occasion not to have been able to photograph the ceiling, but unfortunately on this most recent occasion my thumb kept slipping on to the shutter button (the camera held at waist level) causing the camera to take multiple shots. What was even more coincidental was the fact that the camera happened to be pointed at the ceiling at the time, and to my amazement I ended up with stitch-able shots which yielded the image shown below.
I generally respect instructions involving art works, and the damage flash can cause - however my camera does not have a flash. In addition, in the Sistine Chapel the ban on photographs originated out of a copyright agreement which has now expired. I tend to evaluate the moral/ethical considerations and apply my own standards, and if I consider that I am causing no harm then I go with my own conscience. I am very happy indeed to have at least some record of one of my "bucket list" items rather than having to rely on my virtually useless memory.