When I was a student I had a summer job as a scaffolders' labourer. One of our jobs was the east end of Kings College Chapel. The very old man who ran the stonemasons came to check our work and as a treat I was allowed up on the roof too.
I said what a privilege it was to be amongst all this ancient stonework. He said 'Don't you worry booy, there's nothing you can see that's more than 50 years old.'
The moral being, I suppose, that the idea in the stones is reproduced generation after generation. It doesn't matter that the current stones crumble.
So, when ISIL has gone away, the ideas at Palmyra can be released once again from the rock.