"One of the most recognizable sites in Hawaii, this volcanic ash cone overlooks Waikiki's coastline—a tectonic memory from an explosion half a million years ago, measuring almost 3,500 feet across. British sailors named it Diamond Head in the 1800s, mistaking calcite crystals in the crater’s soil for jewels. Despite its volcanic grandeur, the ascent takes most hikers an hour or so, clocking in at 560 feet of elevation gain and 1.6 miles round-trip. At the top, on a clear day, you can see all of Oahu's south shore, from Koko Crater and Waikiki to the mountains of the Wai'anae Range."