20th Century 
Crow's Nest was a UNSC base in Kenya, Africa, close to the town of Voi. It was a command center for local UNSC Defense Forces in Kenya late in the Battle of Earth. The base was under command of Commander Miranda Keyes.
The Base is located inside Chawia hill, one of the Taita hills, about 24 kilometers west from Voi, Kenya, a few kilometers north of the Tsavo Highway. The Crow's Nest was built for a war in the 20th century, and because of its age, the base often frustrated UNSC personnel because it required constant maintenance and employed outdated technology, such as its door controls.
It was used during the Battle of Voi for its proximity to what the UNSC thought was the Ark (Which in reality was the Portal), as well as the fact that its underground location provided relative protection from aerial and orbital bombardment. From it, the UNSC coordinated its resistance efforts in the region surrounding the remnants of New Mombasa and the local countryside.
The Crow's Nest was originally constructed for use during the 20th century for an unspecified conflict. In some places, a NATO compass can still be seen on the walls. During the occupation of Earth from October to November 2552, it became a base of asymmetrical warfare for human forces in East Africa, because of its prime location deep in the African jungle.
Battle of Voi
- Main article: Battle of Voi
Many wounded marine survivors from encounters with Covenant patrols were sent to the base for medical treatment. The few able-bodied soldiers were organized into fire teams, but were spread thin throughout the base.
When Master Chief John-117 arrived at the base, Fleet Admiral Hood briefed him and the command staff at the base, including the Arbiter and Sergeant Major Avery Johnson about a low-level assault on Covenant Loyalist warships stationed over the so-called "Ark". However, their communication systems were hacked into and the humans received a transmission from the Prophet of Truth, who declared that humanity was doomed to destruction, thus initiating his assault on the Crow's Nest. The UNSC moved to evacuate the facility, electing to destroy the base once they had fled their Covenant attackers. John-117, Gunnery Sergeant Marcus Stacker, Gunnery Sergeant Reynolds, and the Arbiter then organized a defense of the base.
In the opening stage of the battle, John-117 and his allies attacked infantry, mainly Grunts and Jackals in a large roadway containing numerous supply trucks and armaments. They then assaulted the barracks, where the Marines were being massacred by Brute forces. They were successful in rescuing the remaining survivors and wiping out their killers. They then advanced on one of the base's hangars controlled by Covenant Loyalist forces, with support by Type-52 "Phantom" Troop Carriers. The UNSC forces then sent in several Pelicans to collect their remaining forces. John-117 was forced to return to the command center when the Brutes attempted to disarm the bomb meant to destroy the base, and quickly reactivated the bomb upon killing the Brutes. With the bomb approaching detonation, John-117 and the remaining stragglers retreated to the elevator, fleeing to the underground motor pool just as the bomb detonated.
The Crow's Nest was reportedly destroyed when the bomb armed by Master Chief detonated. However, the motor pool and the cave leading to the Tsavo Highway are still intact, having only received minor damage after the explosion. The smoking hangars leading into the Crow's Nest are still visible from the outside.
- Operations Center
- Pipe Room
- South Hangar
- Motor Pool
- Landing Pad Bravo
- Service Elevator
- Ventilation Hub
- Corridor MH1260
- Corridor M70
- Air Turbine 77 (adjacent to 88)
- Air Turbine 88 (adjacent to 77)
- The name "Crow's Nest" originates from a ship's lookout position, located near the mast.
- The Crow's Nest and Voi are the only specific locations that are each featured in two different levels in the Halo 3 campaign.
- In the final cutscene of the previous level, Crow's Nest is wrongly depicted to be located near the base of Mount Kilimajaro, when actually it is at least 90 kilometers to the East.
- In the control room, there are several crates. A few of these have "2401" and "16807". These are most likely references to Bungie's favorite number, seven.