"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.
My interactions with Sorkin were agonisingly weird. He is by far the weirdest person I have ever met. I had dinner with him and a few hours before I got an e-mail from his assistant saying, 'Sean, this does not need to be a long conversation. Aaron is only going to use it to win your trust.'