I spent half an hour in the National History Museum (NHM) vault this morning. Alone with 296 diamonds; the Aurora Pyramid of Hope is a glittering display of extremely rare stones in every color of the rainbow. They even glow in the dark.
As soon as the museum opens, I make a beeline to the gem room before anyone else gets there. I know I am almost guaranteed half an hour before anyone else discovers the room. The vault is situated at the far end of the rocks and minerals room in a quiet corner of the museum.