This ONI Base is a UNSC Office of Naval Intelligence base in the jungles of the planet Arcadia. It is located in close proximity of the Arcadia Forerunner Ruin site. It’s unknown if this is a coincidence, or if the ONI built the base in the area to investigate the ruins.
During the First Battle of Arcadia in 2531, the base was apparently attacked by the Covenant during the opening stages of the battle, as much of the base was left in ruins. The UNSC used the landing area of the apparently-deserted base as their base of operations, when they attacked a Covenant base inside a dome-shaped energy shield. They used an air pad on the base to call in Rhino tanks from the UNSC Pillar of Autumn in orbit, and placed the tanks on the landing pads on the edge of the cliffs. After a few unsuccessful attempts, they managed to destroy the Covenant outposts in the area and breach the energy field. After destroying it, they proceeded down to the valley to investigate the area.
The base is built onto a plateau, likely called "Beasley's Plateau", its edge overlooking the valley that contains the Forerunner ruins. The landing area consists of five landing platforms, all of which are connected to a large central field. The section has two Reactors powering it. It also has a hangar and several other buildings around it, as well as tunnels that lead to other sections of the base. There are also multiple air control towers around the landing area.
The base also extends more along the plateau, having several more installations, mostly roads, fields and air control towers as well as large bunker-like structures.
- The Halo Wars campaign level Dome of Light is set in the base, as well as the multiplayer map Beasley's Plateau.