Yeah, for one, you can actually enter the palace and not stay outside. The numbers of visitors in versailles absolutely dwarfs british palaces. I'm talking 'more visitors[0] than the british top 10 combined[1]'.
And the fee to enter is not cheap. 20€.
There are not many countries who did nuclear weapon tests and even those that did, did not do it in such numbers. Maybe russia, but I doubt that would push the numbers much.
http://www.printadrink.com/
it seems some company did it. (seen in the comments of the blog)