Could it be Alexander the Great’s final resting place?
They’ll have to ask his mummy.
Al's sarcophagus was lost around the time the caliphate conquered Egypt. Possibly it was destroyed, possibly (and reputedly) it was hidden (doors bricked up and concealed), and it's even possible that, despite the rumors that it is still kept hidden by Coptic priests, it slid into the drink during the earthquake that destroyed the Pharos lighthouse.