"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 group consists of 18 main islands, 3 smaller islands, and 107 islets or rocks. The largest of the islands is Isabela which makes up nearly three-quarters of the total land area of the Galapagos islands at 5,827 km² (2,250 mi²).