The island's main museum is small but does an excellent job of putting the moai in their cultural context — the canoes, the petroglyphs, the rongorongo script that nobody has fully deciphered, and the day-to-day life of the people who carved the statues. Exhibits are bilingual in Spanish and English.
The single most important object is one of the few surviving moai eyes — a piece of white coral with an obsidian pupil, recovered from Anakena in 1978. It was this find that proved the moai had once been finished with eyes that brought them to life. The museum is free and a sensible first stop on any visit to the island. Allow an hour.