- Where
- South-east Oʻahu, Honolulu,
Hawaiʻi, United States - Coordinates
- 21.263° N
157.815° W (US Geological Survey) - Formed
- About 300,000 years ago,
in a single eruption (State Parks) - Summit
- 761 feet (232 m)
(State Parks) - Summit trail
- 0.8 mile one way, climbing
560 feet (State Parks) - Entry
- Non-residents: reservation,
$5 a person, $10 a car - Best visited
- Open all year; whales may
pass in winter (State Parks) - Advisory
- Domestic: no State Department
advisory applies
Walked into a mountain through a tunnel, a strange way to arrive anywhere, and found it hollow and dry inside: thorny little trees, warm wind. Then switchbacks, steep stairs, a dark passage, a concrete room with slots for eyes. I squeezed out through one, and below me a city of white towers curved round turquoise water dotted with surfers. I forgot to write anything down for quite a while.
The short answer
Diamond Head State Monument is a park of Hawaiʻi’s Department of Land and Natural Resources (DLNR) in Honolulu, on the island of Oʻahu, at the eastern edge of Waikīkī’s shore. Its Division of State Parks says the monument covers more than 475 acres, including the inside and the outer slopes of the crater, whose Hawaiian name the division spells Lēʻahi. The crater is a tuff cone, formed about 300,000 years ago in a single explosive eruption, by the division’s account; the US Geological Survey lists the Diamond Head tuff cone among the Honolulu Volcanics, of Pleistocene age. A trail built for the US Army in 1908 climbs 0.8 mile and 560 feet from the crater floor to the summit, through a lit tunnel and up steep stairs to a fire control station completed for the coastal defence of Oʻahu. Visitors who are not Hawaiʻi residents must book a timed entry, and parking, in advance.
Why it's worth knowing
A crater made in one go. Oʻahu, the Division of State Parks explains, began about 2.5 to 4 million years ago as two shield volcanoes, which eroded into the Koʻolau and Waiʻanae ranges. After about 1.3 million years of quiet, the south-eastern end of the Koʻolau Range erupted again, this time under the ocean, where water and steam broke the magma into ash and fine particles; blown into the air, they settled and cemented into tuff. Lēʻahi is believed to have formed that way in a single, brief eruption, the division’s brochure says. Its crater covers 350 acres and is wider than it is high, and its south-western rim stands highest because the wind was blowing the ash that way while it fell. The brochure records that Diamond Head was made a National Natural Landmark in 1968 as an excellent example of a tuff cone.
April 2013The floor of the crater from the air.
Photograph: Eric Tessmer via Flickr · Diamond Head from above · CC BY 2.0 · cropped
A summit hollowed out for the Army. The federal government bought Diamond Head in 1904 for military use, and fortification began in 1908, the brochure says, with gun emplacements and a tunnel through the crater’s north wall. The trail to the summit was built that year for mules and men hauling material up to the fire control station. The National Register nomination for the Fort Ruger Historic District, written by DLNR’s historians in 1980, calls that four-storey station the most elaborate structure of its kind in the United States, because most fire control stations were simple free-standing towers of metal, and credits its design and construction to Major E. E. Winslow, who graduated first in West Point’s class of 1889. Diamond Head was ready to defend Oʻahu, the brochure says, but no artillery was ever fired from it in war.
The field notes
Two names for one hill
The Division of State Parks’ brochure gives the Hawaiian name two readings. It is said that Hiʻiaka, sister of the fire goddess Pele, named the summit Lēʻahi because it resembles the forehead, lae, of the ʻahi fish; another translation is “fire headland”, for the fires lit at the summit to guide canoes travelling along the shore. A heiau, a temple, on the summit was dedicated to the god of wind, the brochure adds, as protection against the strong updrafts that could put those fires out. The English name came later. In the late 1700s, by the brochure’s account, Western explorers and traders mistook the calcite crystals in the rocks of the crater’s slope for diamonds.
Four floors behind the rock
The fire control station at the summit has four levels, linked by a spiral iron staircase, the Fort Ruger nomination records, each with observation slots 12 inches high that were once closed by moveable steel shutters. Its outside was camouflaged with rubble set in concrete, paint and rock dust. The lowest level directed Battery Randolph at Fort DeRussy in Waikīkī; the next served Randolph and Battery Dudley there; the third commanded Battery Harlow at Fort Ruger, on the crater’s outer slope; and the top floor was the battle commander’s station, 761 feet above sea level, with a view of the coast from Koko Head to Waiʻanae. The sources differ by a year on its date: the nomination and the division’s brochure say it was built between 1908 and 1910, and the division’s park and trail pages say it was completed in 1911.
October 2014From the summit rim: the old fire-control station's roof, Kapiʻolani Park, Waikīkī and the coast.
Photograph: Ron Cogswell via Flickr · Honolulu (HI) Looking West From the Diamond Head Summit October 2014 · CC BY 2.0
Fort Ruger and its batteries
The Army post behind the crater was named for Major General Thomas H. Ruger, a Civil War veteran and former superintendent of West Point, the nomination says. Two Coast Artillery companies moved in on 14 August 1909, living in tents, and on 17 March 1910 they took over Battery Harlow, a bunker for eight 12-inch mortars and the first of Oʻahu’s coast-defence works to be completed. Until 1913 Fort Ruger was the only garrisoned coast artillery fort in the islands, and until 1921 it was the headquarters of the Coast Defenses of Oʻahu. Batteries Hulings and Dodge followed in 1915, tunnelled through the crater wall; Battery Birkhimer, largely underground on the crater floor, in 1916; and Battery 407, facing the sea, was begun in 1943. With the end of the Second World War and the arrival of missiles the batteries became obsolete, and in December 1955 most of the land passed to the State of Hawaiʻi. The crater is still Department of Defense ground after hours: the reservation site says that after 6 pm the park is secured by the Department of Defense.
Counting the steps
The division’s 2012 brochure numbers the trail’s features. The trailhead on the crater floor is about 200 feet above sea level. The path still follows the 1908 alignment, in switchbacks up the inside slope, past the concrete landing that once held a winch and cable for lifting material from the crater floor. A stairway of 74 concrete steps leads into the first tunnel, which is lit and 225 feet long; a second stairway of 99 steep steps follows, under overhead beams that once carried camouflage, to the lowest level of the station. Inside, 52 stairs on the spiral staircase climb to the third level, and 54 metal stairs, put in during the 1970s in place of a ladder, reach the summit. The way down the rim is 82 metal steps. The division’s current park page says only that the last tenth of a mile is all stairs and especially steep.
October 2014The concrete stairs of the summit trail between rock walls.
Photograph: Ron Cogswell via Flickr · Steps on the Diamond Head Summit Trail -- O'ahu (HI) October 2014 · CC BY 2.0
The ridge of Diamond Head over open water.
Photograph: Colin + Meg via Unsplash · Unsplash licence
December 2014Diamond Head Lighthouse on the slope above the reef.
Photograph: Edmund Garman via Flickr · Diamond Head Lighthouse From Above · CC BY 2.0
- Sort out your ticket before you come. The gate is very polite about it, and very firm.
- Go early, while the switchbacks are still in shade, and climb at the pace of whoever is in front of you. Everybody arrives at the top eventually.
- Read the list at the summit. (Read the first item, looked up, saw the whole coast, and put the list back in my pocket for an hour. Item two is still waiting, very patiently.)
- Look out to sea as well as down at the beach, and give it a few minutes. Something large may come up and breathe, a long way off.
- This hill was somebody’s long before anybody dug a lookout into it. Learn what they called it, and say the name properly at the top.
An observation slit in the fire control station at the summit of Diamond Head. The station’s four levels each have observation slots 12 inches high, once closed by moveable steel shutters, from which soldiers watched the sea and directed the fire of the batteries at Fort DeRussy and Fort Ruger, the 1980 National Register nomination for the Fort Ruger Historic District records; the Division of State Parks’ 2012 brochure sent hikers out through those slits onto the summit. No artillery was ever fired from Diamond Head in war, the brochure says.
Tally, in the marginI climbed out through it as if it were a door, and it was halfway down the hill before it occurred to me that it was made for watching, not for leaving. Somebody once stood behind it looking at that same bright sea and hoping very hard to see nothing at all. I hope they noticed the view.
Getting there
How to get there. The entrance is off Diamond Head Road between Makapuʻu Avenue and 18th Avenue in Honolulu, the Division of State Parks says, and the trailhead is beside the car park on the crater floor. Cars reach the floor through a tunnel in the crater wall, the Kahala Tunnel, which the brochure dates to the 1940s; the Fort Ruger nomination describes the vehicle tunnel as built during the Second World War. Parking in the crater is very limited, the reservation site says: a parking reservation is for a set period and the car must leave by its end, while visitors who walk in or are dropped off may stay until they finish. Everyone must be out through the tunnel by 6 pm. Tour companies and commercial carriers use a separate reservation system.
May 2010The lit road tunnel through the crater wall.
Photograph: Daniel Ramirez via Flickr · Diamond Head Tunnel · CC BY 2.0 · cropped
When to go. The park opens daily from 6 am to 6 pm and closes on Christmas Day and New Year’s Day. The last reservation is for 4 pm, and its last entry is 4:30 pm. The division’s brochure says the weather here is always hot, and it recommends a hat, sunscreen and plenty of water. From the summit in winter, the division says, the view may include passing humpback whales. The sources give different times for the climb: the park page says to allow 1.5 to 2 hours, the trail page gives 2 hours, and the reservation site says the hike typically takes 60 to 90 minutes.
What to arrange ahead. Since 12 May 2022, visitors who are not Hawaiʻi residents have needed an entry reservation, and a parking reservation if they bring a car, the division says; anyone without one is turned away. Bookings open up to 30 days in advance on the state’s reservation site, gostateparks.hawaii.gov, and the site warns that the park can sell out. Entry is $5 a person and parking $10 a vehicle, by credit card only; children aged 3 and under enter free, and there is no military discount. Residents with a Hawaiʻi ID or driving licence enter free without booking, but their visitors from out of state must book. Arrive within the first 30 minutes of the reservation or entry may be refused; refunds are allowed up to 3 days before the visit, and none is given for bad weather unless the park officially closes.
Access. The facilities on the crater floor are fully accessible, the division says; the summit trail is not ADA accessible, and is very steep and uneven in places. The first 0.2 mile is a concrete walkway, after which the path becomes natural tuff, with steep stairs and a long, narrow, lit tunnel. No pets are allowed in the park except service animals, and hiking groups of 25 or more need a permit.
Safety. The State Department’s travel advisories cover other countries, so none applies here; the hazards are the park’s own. The division describes the climb as steep and strenuous and asks hikers to stay on the trail, wear good walking shoes, and call 911 in an emergency. The central Pacific hurricane season officially begins on 1 June and ends on 30 November, the Central Pacific Hurricane Center says, and state parks close for storms: DLNR refunds day-use reservations for any day that was part of a storm-related closure. The division’s park notices of 23 October 2026, read on 25 October 2026, listed closures elsewhere on Oʻahu during the recovery from Hurricane Nolo and Hurricane Lowell, and none at Diamond Head.
Mark this place
Common questions
Do you need a reservation to hike Diamond Head?
Yes, unless you are a Hawaiʻi resident. Since 12 May 2022, visitors who are not Hawaiʻi residents have needed a timed entry reservation for Diamond Head State Monument, and a parking reservation if they bring a car, the Division of State Parks says. Reservations open up to 30 days ahead on gostateparks.hawaii.gov, and visitors without one are turned away.
How much does it cost to visit Diamond Head?
Diamond Head State Monument charges visitors who are not Hawaiʻi residents $5 a person to enter and $10 a vehicle to park, by credit card only, according to the Division of State Parks. Children aged 3 and under enter free, and Hawaiʻi residents with a state ID or driving licence enter free.
How long is the Diamond Head summit trail?
The Diamond Head summit trail is 0.8 mile (1.3 km) each way, 1.6 miles in all, and climbs 560 feet (171 m) from the crater floor, the Division of State Parks says. Its last tenth of a mile is all stairs, and the division’s park page says to allow 1.5 to 2 hours for the hike.
What are the opening hours of Diamond Head State Monument?
Diamond Head State Monument opens daily from 6 am to 6 pm, the Division of State Parks says, and closes on Christmas Day and New Year’s Day. The last reservation is for 4 pm, the last entry is at 4:30 pm, and the gates are locked at 6 pm.
How was Diamond Head formed?
Diamond Head, or Lēʻahi, is a tuff cone that formed about 300,000 years ago in a single explosive eruption, according to Hawaiʻi’s Division of State Parks: ash and fine particles thrown into the air settled and cemented into a rock called tuff. The US Geological Survey lists the Diamond Head tuff cone among the Honolulu Volcanics.
Why is it called Diamond Head?
Diamond Head got its English name in the late 1700s, when Western explorers and traders mistook calcite crystals in the rocks of the crater’s slope for diamonds, the Division of State Parks’ brochure says. The Hawaiian name, Lēʻahi, is said to come from the summit’s likeness to the forehead of the ʻahi fish.
What is at the top of Diamond Head?
At the top of Diamond Head is a four-storey fire control station built for the US Army’s coastal defence of Oʻahu, from which observers directed the guns of Fort DeRussy and Fort Ruger, the National Register nomination for the Fort Ruger Historic District records. Hikers reach it through a 225-foot lit tunnel and up steep stairs.
When is hurricane season in Hawaii?
The central Pacific hurricane season, which covers Hawaiʻi and Diamond Head, officially begins on 1 June and ends on 30 November, the Central Pacific Hurricane Center says, though storms can form at other times. Hawaiʻi’s state parks close for storms, and DLNR refunds reservations made for a day of storm-related closure.