Diamond Head is the name of a volcanic tuff cone on the Hawaiian island of Oʻahu and known to Hawaiians as Lēʻahi, most likely from lae ‘browridge, promontory’ plus ʻahi ‘tuna’ because the shape of the ridgeline resembles the shape of a tuna’s dorsal fin. Its English name was given by British sailors in the 19th century, who mistook calcite crystals embedded in the rock for diamonds. Diamond Head is estimated to be about 200,000 years old and extinct for 150,000 years. (Source: Wikipedia)
Diamond Head offers you great view over Honolulu, Waikiki and Koʻolau Mountain Range.