Diamond Head Tunnels

Visitors to Diamond Head pass through two tunnels. The Kahala Tunnel, built through the crater wall in the 1940s, is the only public way into the crater, by car or on foot; its gate closes at 6 p.m. and reopens at 6 a.m. On the summit trail, a lighted tunnel 225 feet long leads to the last stairs and the Fire Control Station.

The Kahala Tunnel (the Way In)

The entrance road leaves Diamond Head Road between Makapuʻu Avenue and 18th Avenue and runs through the Kahala Tunnel to the crater floor. It was built in the 1940s and is the public entrance today. Cars, walk-ins and drop-offs all use it, which is one reason the state limits numbers: congestion in this single access tunnel was one of the problems the 2022 reservation system was meant to fix.

Gate times: the tunnel gate closes at 6 p.m. and reopens at 6 a.m. Everyone must be out through the tunnel by 6 p.m., after which the Department of Defense secures the park. See hours.

The Trail Tunnel

On the upper part of the hike, a 74-step concrete stairway leads into a narrow tunnel. It is lighted and 225 feet long, according to Hawaii State Parks. Past it, a second stairway of 99 steep steps climbs to the Fire Control Station. It is narrow, so expect to pass people coming the other way.

The Kapahulu Tunnel (Historic)

The first tunnel into the crater was the Army's Kapahulu Tunnel, cut through the north wall from Fort Ruger when fortification began in 1908. The summit trail started from it, climbing the steep western slope of the crater interior. It is not the public entrance.

Battery Tunnels

Several of Diamond Head's coastal batteries were dug into the rock. Batteries Dodge and Hulings (1913) tunnel through the eastern crater wall, and Battery 407 (1943) tunnels through the southern wall and faces the sea. None is on the visitor route. See military history.