The charmed roof of the great hall was definitely impressive but the fact no one had seemed to have read there books already since it was clearly stated in Hogwarts a History that it had been charmed by the foundered to reflect the sky above it, apparently it was something that had never been replicated on such a scale since, the fact it had lasted since there deaths had amazed many researchers who couldn't understand what exactly they did to it. The fact no Headmaster had allowed extensive study of Hogwarts didn't help things at all. Apparently Hogwarts was considered separate from the control of the Wizengamot and by extension the Ministry of Magic.