A Heiau is a Hawaiian Temple were used to worship and sacrifice.  Heiaus were erected to go along with ancient Hawaiian myths and legends.  Heiaus were used to ensure one's health, the nation's health, to achieve success on the battlefield, agricultural purposes,  and other beliefs.  These sacred temples were either erected out of earth material such as wood and ti leaves, or they were erected out of stone.

This is a picture of the Hale O Pi'ilani Heiau near Hana, Maui.  This is the largest Hawaiian Heiau, and I have actually been to this one.