"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.
But I now entered on my fifteenth year - a sad epoch in the life of a slave girl. My master began to whisper foul words in my ear. Young as I was, I could not remain ignorant of their import.