Research indicates there are 25 ancient sites on the island, most of which are difficult to access and have not yet been restored; others were destroyed when the air base was built in the 40s. The most famous site is San Gervasio, with its six clusters of buildings spread over an area of three square kilometers. Some of the buildings are of considerable height, and set upon grand platforms. The site is located in the middle of the island and is accessible from the cross-island highway.
The other site worth mentioning is El Cedral, where the original stucco and color applied by the ancients are still visible.