"Ahu" are stone platforms on which many moai sit. There are 313 known ahu and 125 of these carry moai. The biggest, Ahu Tongariki is 220 m (720 ft), and had the most (15) and tallest moai.
There's a lot of interest from the medical community on how things develop in microgravity, and the hope, later, that is expected to apply to what the changes are in humans as well.