HOW THE CRATER WAS FORMED
THE EARLY HISTORY
The pronounced seaward summit, deeply
eroded ridges, and ovoid-shaped crater are evidence
of Lë‘ahi’s very dynamic geological history. The
creation of O‘ahu began around 2.5 to 4 million
years ago with volcanic eruptions from 2 shield
volcanoes. A period of extensive erosion followed,
leaving the Ko‘olau and Waiçanae Mountain Ranges
as the remnants of these volcanoes.
After about 1.3 million years of volcanic
inactivity, the southeastern end of the Ko‘olau
Range erupted. These eruptions occurred under the
ocean, where the magma was broken down into ash
and fine particles by the water and steam. Blown
into the air, these particles were cemented together
into a rock called tuff which created tuff cones, such
Lë‘ahi is believed to have been formed about
300,000 years ago during a single, brief eruption.
The broad crater covers 350 acres with its width
being greater than its height. The southwestern rim
is highest because winds were blowing ash in this
direction during the eruption. Since the eruption, the
slopes of the crater have been eroded and weathered
by rain, wind, and the pounding of the sea. A coral
reef now protects the seaward slopes of the crater.
Today, Lë‘ahi (Diamond Head) is the most
recognized landmark in Hawai‘i. It was designated
a National Natural Landmark in 1968 as an excellent
example of a tuff cone.
It is said that Hi‘iaka, sister of the fire goddess
Pele, gave Lë‘ahi its name because the summit
resembles the forehead (lae) of the ‘ahi fish. Another
translation is “fire headland” and refers to the
navigational fires that were lit at the summit to assist
canoes travelling along the shoreline. The heiau
(temple) built on the summit was dedicated to the
god of wind as protection against strong updrafts
that could put out these navigational fires. Today,
the Diamond Head Light, built in 1917, provides a
visual aid for navigation.
In the late 1700s, Western explorers and traders
visited Lë‘ahi and mistook the calcite crystals in the
rocks on the slope of the crater for diamonds. Thus,
the name Diamond Head became the common name
for the crater.
The semi-arid climate, the steep
rocky slopes, and the shallow soil of
Diamond Head support mostly low
shrubs and herbs. Botanists believe
that the crater was once covered by
a dryland forest, but only a few native
Hawaiian species, such as ‘ilima, remain.
Rainwater collects on the crater floor in the winter,
creating a small lake that was frequented by native
ducks and waterbirds until the early 1900s.
Most of the plants and animals you see in the
crater today were introduced to Hawai‘i after the
1800s. Dominant plants are the kiawe, a relative of
the mesquite, and koa haole. Both of these plants
were brought in as cattle feed and have adapted
well to the hot, dry conditions. You may see some
of the common introduced birds, such as cardinals,
doves, and sparrows.
From this observation station, observers could
triangulate targets and aim artillery and mortar fire
from Batteries Randolph and Dudley at Fort DeRussy
in Waikïkï and Battery Harlow at Fort Ruger on the
outer slopes of the crater. Consisting of 4 levels, the
exterior of the Fire Control Station was camouflaged
with rubble embedded in concrete. Slits with metal
shutters on each level provided seaward viewing
for potential sea and air attacks. The 4 levels and
the summit were accessed by a spiral staircase and
ladders between the levels.
Additional coastal defense was provided by
long range guns installed on the outer slopes and
rim of the crater around 1915. Diamond Head
was prepared to defend O‘ahu from attack but no
artillery was ever fired during a war.
The military features of Diamond Head are part
of the Fort Ruger Historic District.
With its panoramic view from Koko Head to
Wai‘anae, the summit of Diamond Head was an
ideal site for the coastal defense of O‘ahu. In 1904,
Diamond Head was purchased by the Federal
government and designated for military use.
Fortification began in 1908 with the construction of
gun emplacements and an entry tunnel through the
north wall of the crater from Fort Ruger known as
the Kapahulu Tunnel.
Batteries were built to house the coastal artillery.
A total of 5 batteries were built at Diamond Head
Crater: Harlow (1910) on the northern exterior,
Dodge and Hulings (1913) which tunnel through
the eastern crater wall, Birkhimer (1916) which is
largely below ground inside the crater, and Battery
407 (1943) which tunnels through the southern wall
of the crater and faces seaward.
Fire Control Station Diamond Head was built
at the summit between 1908-1910 and housed
instruments and plotting rooms to direct artillery
fire from several batteries. This fortification was an
engineering marvel of its time.
Department of Land & Natural Resources
DIVISION OF STATE PARKS
1151 Punchbowl Street, Room 310
Honolulu, Hawai‘i 96813
Phone: (808) 587‐0300
HISTORIC TRAIL TO THE SUMMIT
POINTS OF INTEREST ON THE TRAIL
The trail to the summit of Lë‘ahi was built
in 1908 as part of the U.S. Army Coastal Artillery
defense system. Entering the crater from Fort Ruger,
through the Kapahulu Tunnel, the trail scaled the
steep interior western slopes of the crater to the
summit. The dirt trail with numerous switchbacks
was designed for mule and foot traffic. The mules
hauled materials on this trail for the construction
of Fire Control Station Diamond Head located at
the summit. Other materials were hoisted from the
crater floor by a winch and cable to a midway point
along the trail. The Kahala Tunnel was built in the
1940s and is the public entrance today.
HIKING THE TRAIL
From the trailhead to the summit of Diamond
Head Crater, you will hike 0.8 mile (1.3 km) one way
and climb 560 feet (171 m) from the crater floor. The
trail follows an uneven and steep terrain requiring
caution and appropriate footwear. Portions of
the trail involve steep stairways - take your time.
Other portions of the trail go through a long tunnel
which is lighted. Allow 1.5 to 2 hours for a safe and
leisurely round-trip hike.
After exiting the tunnel, turn right and take
the 99 steps into the Fire Control Station up to the
summit. To avoid congestion, take the loop trail
along the rim and interior slope back to the tunnel.
HAVE A SAFE HIKE
The weather here is always hot - a hat, sunscreen
and plenty of water are recommended.
• The tunnel gate closes at 6:00pm (1800 hours)
and reopens at 6:00am. Do not get locked in!
• Last time to start the hike is 4:30pm.
• Pack out what you pack in - do not litter.
• Do not deface the historic structures.
• Do not enter closed or
• In case of emergency,
Following the numbers
on this map, you will
make a one-way loop at
the summit. This will
reduce congestion and
The elevation at the trailhead on the crater floor
is about 200 feet (61 m).
The former pistol ranges consist of earthen berms
that are visible from the concrete path.
The trail conforms to the 1908 alignment with
switchbacks up the steep interior slope.
Concrete Landing/Lookout. This concrete
foundation held a winch and cable to lift
materials from the crater floor to this point.
Steep stairway of 74 concrete steps leads into the
first narrow tunnel.
Tunnel is lighted and 225 feet long.
Second stairway consisting of 99 steep steps with
overhead beams to place camouflaging.
At the top of the stairs is the entry to the lowest
level of the Fire Control Station with observation
equipment for Fort DeRussy at Waikïkï.
The lighted spiral staircase accessed the 4 levels
of the Fire Control Station. Go up the 52 stairs
to the third level where the mounts for the
observation equipment are still present.
10 Exit to the exterior of the crater through slits once
covered with metal shutters. Note the rock and
concrete that camouflage the outside.
11 The 54 metal stairs were installed in the 1970s
and replaced the ladder to the summit.
12 The elevation of the crater summit and the
uppermost level of the Fire Control Station is
761 feet (232 m).
13 From the summit, follow the trail along the rim
and take the 82 metal steps down to the lower
trail. This trail loops back to the tunnel.
14 Bunkers along the crater rim were built in 1915.
Area closed - emergency helicopter landing.
Lëçahi is a fragile resource. By
staying on the trails and not taking
shortcuts, you save plants and
15 Lookout provides sweeping views of southeastern
O‘ahu coastline towards Koko Head and the
offshore islands of Moloka‘i, Lana‘i and Maui.
16 Rest stop offers views of the crater before
heading back down through the tunnel.