"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 iconic David Bowie section on the smash hit "Under Pressure" almost never happened as this wasn't actually planned. Bowie was simply in the studio at the time and decided to get involved.