Rising 232 metres above the southeastern shore of Oahu, this volcanic tuff cone is Hawaii's most recognisable natural landmark, its distinctive profile visible from virtually every elevated point in Honolulu and Waikiki. The crater was formed approximately 300,000 years ago in a single explosive eruption that lasted only days, as rising magma encountered shallow groundwater and coral reef, producing a phreatomagmatic blast that deposited ash and limestone fragments in the ring shape visible today. The Hawaiian name is Leahi, meaning brow of the tuna, describing the profile of the ridgeline as seen from the west. The English name derives from nineteenth-century British sailors who mistook calcite crystals glinting on the slopes for diamonds. The US military fortified the crater from 1908, constructing Battery Harlow and fire control stations connected by tunnels through the rim, part of the coastal defence system protecting Honolulu Harbour and Pearl Harbor beyond. The 2.6-kilometre summit trail, opened to hikers in 1908 using military switchbacks, climbs 171 metres from the crater floor through two tunnels and a 99-step staircase to the observation platform atop the western rim. The reward is a 360-degree panorama encompassing Waikiki Beach, the Ko'olau Range, the South Shore reefs, and on clear days the neighbouring islands of Molokai and Lanai. Diamond Head State Monument requires advance reservations due to overcrowding concerns, with timed entry slots limiting trail access. The crater interior contains a military installation still in active use. The surrounding slopes and coastal trail system provide additional walking routes at lower elevations. TheBus route 23 connects Waikiki to the trailhead entrance on Diamond Head Road. The crater floor was designated a National Natural Landmark in 1968. The surrounding residential neighbourhood of Diamond Head is among the most expensive in Honolulu, with properties on the crater's outer slopes commanding premium values for their proximity to both the landmark and Waikiki.

Type: Outdoors

Address: Diamond Head Road, Honolulu, United States, 96815