This sign greets visitors to Mo’okini heiau. The heiau dates back to the 11th or 12th Century when it was an important religious site where thousands of human sacrifices were carried out. A hazardous area indeed. I imagine there were many who would happily have risked climbing the walls in those days.
For more information about the Mo’okini heiau, go to bigislandhikes.com/mookini-heiau/.