Sunholes

The Sunholes were holes in Lake Naho in Ga-Koro and somewhere in Mount Ihu in Ko-Koro. They let light shine in from the island of Mata Nui to Metru Nui. The sunholes closed when the Great Cataclysm took place, but since opened when Mata Nui was revived by Matoro wearing the Kanohi Ignika.

Trivia

 * The Sun Holes were actually The Great Spirit Robot's Eyes.