Are you referring to "1. OBSERVATORY. In the center, a stone sphere resembling the moon."?
As I read this (incorrectly apparently haha), I thought it was referring to something much larger if PC's can squeeze through the hole.
In area 6 LADY STATUE the statue appears human-sized in the illustration. She is holding a moonstone, implying it is small enough to hold in one hand.
This might be the point of confusion?