"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.
The Carter Center has the only existing international taskforce on disease eradication. Which means a total elimination of a disease on the face of the Earth. In the history of the world, there's only been one disease eradicated: smallpox. The second disease, I think, is gonna be guinea worm.