The Hawaiian name for Diamond Head is Le'ahi. It is a tuff cone (consolidated volcanic ash) crater that was created 300,000 years ago during a single volcanic eruption that spewed ash into the air.

It includes Geomunoreum, regarded as the finest lava tube system of caves anywhere, with its multicoloured carbonate roofs and floors, and dark-coloured lava walls; the fortress-like Seongsan ...