"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.
A generous prayer is never presented in vain; the petition may be refused, but the petitioner is always, I believe, rewarded by some gracious visitation.