Diamond Head State Monument (Le'ahi) is Waikiki's most recognizable landmark and the island's most-hiked trail. The 0.8-mile path climbs 560 feet from the crater floor to a 762-foot summit, passing through a 225-foot tunnel and up 99 narrow concrete stairs built by the US Army in 1908 as part of Fort Ruger's coastal defense system. From the top, hikers get a postcard panorama spanning Koko Head to Wai'anae, with humpback whales sometimes visible offshore in winter. Non-resident visitors must reserve entry and parking online up to 30 days in advance through Hawaii State Parks; entry is $5 per person plus $10 per vehicle. Plan 1.5 to 2 hours round trip, go early to beat heat and crowds, and bring water, sturdy shoes, and sun protection.
"Views are absolutely worth the effort. We started at 7 a.m., beat the heat and the crowds, and had the summit nearly to ourselves. The 99 stairs and tunnel are no joke but very doable if you take your time."