Diamond Head is a 500,000 year old volcanic tuff cone on the Hawaiian island of Oʻahu. The name was given by British sailors in the 19th century, who named it for the calcite crystals on the adjacent beach. From above, it looks like a lost world, but this green crater carved into the cliffs is very real. One eruption. One crater. A half-million years of silence... and now? It's a place where tourists hike, history lives, and the view is out of this world. Would you like to visit this remarkable, green volcanic crater?