Halo Alpha
Halo Alpha

Were you looking for the level "The Ark" or for the Greater Ark, creator of the original twelve Halo rings?

“Where would someone go to activate the other rings?”
“...Why, the Ark, of course.”

Installation 00, also known as The Ark[3] or The Lesser Ark,[4] is an enigmatic Forerunner installation from which all the Halo Installations across the galaxy can be activated simultaneously.[3] In addition, it functions as a safe haven from the Halo network's strategic pulse, as well as a facility to construct and repair any of the Halo Array.


This section requires expansion.

Forerunner-Flood war[]

Main article: Forerunner-Flood war

The Ark sending the Halo Array through Slipspace during the Forerunner-Flood war

Installation 00 is a part of the Forerunner construct designed to wipe the Flood from the Galaxy. Located about 218 (262,144) light years from the galactic center,[1] Installation 00 is located outside the galaxy and is thus safe from the Halo effect (as it is referred to by the Forerunners in the terminal transcripts) that kills all organic sentient lifeforms. The main Forerunner behind its use was the Iso-Didact. The commission of this installation is to remotely activate the seven Halo rings then in existence, from outside the pulse radius of the array. This is a fail-safe system, and is only activated by an aborted firing such as the one that occurred at the end of the Battle of Installation 05 (Delta Halo). In addition, Installation 00 can also function as an automated factory to construct replacement Halo installations, thereby ensuring that the Halo array is always ready to fire, should the array be needed.

“Every vessel we can fill, we send to the Ark. I dare not cease the mission. Not now, not until I've done all I can. Each one of these souls is finite and precious.”
— Transcript of a message from the Librarian to Ur-Didact, interpreted post-cataclysm and retrieved from the first Terminal on the level "The Ark"

During the construction of the Halo Array, while the rest of the Forerunners civilian and military presence attempted to defeat the Flood through any way they knew possible, a plan B was also approved by the Ecumene Council, which included the construction of the Shield Worlds like Onyx, and The Arks.

With this final push, a last ditch plan for the defeat of the Flood, The Librarian was to index every sentient species in the Galaxy, and bring many of the more intelligent species to the Arks, and then presumably key Forerunners would take refuge within the Ark's secret location, until the Flood were starved and they could go return to the Milky Way Galaxy.

However, things did not go as planned, as the Forerunner military AI 032 Mendicant Bias turned on the Forerunners after considerable convincing from a Gravemind, and began assisting the Flood. Mendicant Bias knew of the Ark, how to access it through Forerunner Key Ships (only Lifeworkers had slipspace privileges at the time due to indexing requirements), but did not know of its exact location outside of the Milky Way Galaxy. The Ecumene Council then commissioned another military AI, Offensive Bias, in order to devise the best possible defense against Mendicant Bias, his fleet, and the impending attack against the Maginot Line. The Librarian scuttled all of the Key Ships under her command.

Human-Covenant war[]

Main article: Human-Covenant war

Attacks on Other Installations[]

When Installation 04 was destroyed at the hands of John-117,[5] the Ark began to build a replacement ring: Installation 08.[6]

When Installation 05 misfired at the hands of the Covenant, a signal was sent to the Ark, putting the whole array into standby mode. Remote activation of the whole array was then possible from the Ark.[3]

Battle for the Ark[]

Main article: Battle of Installation 00
H3 E3 Orbital Battle

The space battle over the Ark.

After the Prophet of Truth's forces escaped Earth through The Artifact, human and Separatist forces resolved to follow him through the portal[7] where they ended up at Installation 00.[8]

Once they arrived on the Ark, the UNSC and the Separatists would battle Covenant Loyalists across the surface of the Installation. This included finding the Installation's Silent Cartographer,[8] finding and killing the Prophet of Truth at the Citadel,[9] and using the newly constructed Installation 08 to destroy the Flood[6] that arrived using an infected High Charity.[9]

After activating Installation 08, the damage to the Installation caused the portal to collapse, cutting the UNSC Forward Unto Dawn in half as it passed through. The forward section, in which Thel 'Vadam had been inside of, made it back to Earth, plunging into an unspecified body of water. The other section of the Forward Unto Dawn, containing John-117 and Cortana, did not make it through the portal, and was left stranded in an unknown location of deep space, drifting towards Requiem.[6]

Post Covenant war[]

The Rubicon[]

After the war, the UNSC sent an investigative group to Installation 00. After launching probes, the group received a Forerunner signal coming from the surface of the Ark. After the team determined the dense debris field to be stable for further activity in the region, the UNSC Rubicon was deployed from Luna to conduct a more thorough investigation of the installation's ravaged surface. Due to the damage dealt to the Ark's life support systems and its artificial sun, heavily inclement weather became common.[10]

The Rubicon had several remote contact teams that landed on the Ark and attempted to find the source of the mysterious signal. After nearly eight days, all contact with the teams was lost. Only one team, RCT-06, returned, having sustained heavy casualties and carrying with them an unknown device. The armature's origin was subjected to debate, but it was believed by the team to be the source of the beacon picked up by the initial investigative group.[10] The device was a broken, barely active monitor which eventually revealed to be 343 Guilty Spark. Claiming that he knew the location of the Librarian, whom he believed to be alive, Spark incorporated the ship's AI, incapacitated the crew via the life support systems, and hijacked the ship.[11] Communications with the Rubicon stopped within 48 hours after last report. Search and rescue teams were then sent to the site, but have, so far, reported no findings.[10]

Return to the Ark[]

Main article: Operation: FAR STORM

In 2555, a joint Human-Sangheili task force returned to the Ark after Earth was attacked by a massive Retriever Sentinel. As well various teams at different Halo Installations realized that the Halos were activating for an unknown reason.[12]

In 2557, another team returned to the Ark in the Eden Rising to activate Retriever Sentinels to assist in repairing and maintaining the Ark. They established the Henry Lamb Research Post and various others to aid in this endeavor. However, in the August of that year, the portal connecting the Ark to Earth, closed. Most of the expedition was destroyed by The Banished.[13]

The Spirit of Fire[]

Main article: Battle of Installation 00 (2559)
This section requires expansion.

In 2559, the UNSC Spirit of Fire arrived at the Ark via slipspace.[14] Here, they encountered the Banished, a Jiralhanae faction vying for control of the Ark.

Design and Function[]


A Holographic representation of the Ark.


The Ark compared to the planet Earth and Halo. (Courtesy of Stephen Loftus)

Installation 00 resembles a massive wheel with a series of eight curved arms retreating from its centre, similar to a sea star and bearing similarities to a sun. The Ark Core is the stripped remnant of a material-rich planetoid, asteroid, or other celestial body used for the construction of the Halos, which the Ark constructs. The entire upper surface is terraformed and has a multitude of environments, with oceans, forests and even a large desert, where John-117 first makes landfall. At the time of construction, the Ark lacked its core and a livable surface with no land or water. The structure is the second largest known Forerunner construct, only dwarfed by the Micro Dyson Sphere and other Shield Worlds (such as Shield 0006) which has a diameter of 300 million kilometers. A simple inspection of the holographic representation reveals the Ark to be anywhere from 90,000 to 100,000 kilometers (55,890 to 62,100 miles) in diameter.[15]

The three shown primary functions of Installation 00 are to act as a remote for activating the entire Halo Array network while safely out of the Halos' range, as an automated construction facility for the creation of replacement Halo installations (ensuring that the network continues to operate even if any rings are destroyed), and it has also been confirmed that the Ark was meant to be used to reseed the galaxy in the event of the Halo Arrays being fired. Held deep within its mysteries was a collection of every species the Forerunners had studied and governed over. How this plan was to be initiated is still unknown, although, gleaning information from how the Milky Way Galaxy was reseeded eventually, the same conventions and constructs would have most likely been used, such as automated data logs for the retrieval and reseeding of the galaxy through means of Forerunner Key ships which were found on several planets in the galaxy such as Earth and the San'Shyuum home world of Janjur Qom.


A view of Installation 00's Artificial Sun.

Most interestingly, the Ark is not actually in the Milky Way.[1][8] The Ark is in the void in between galaxies, known as intergalactic space. As such, it's outside the believed range of any Halo installation. The Ark also has an artificial sun floating above it.


Ark surface 3

A view of the Ark's arms from the surface. The Ark's artificial sun can be seen in the sky.

Along with most Forerunner constructs, the Ark consists of an atmosphere similar to Earth, comprised of mostly Oxygen and nitrogen. This means all Humans, all Covenant species (excluding Unggoy who depend on methane tanks to survive) and the Flood are able to live on the installation. Also, like Earth and the other Installations, weather can radically change on the Ark.

The Ark has a habitable surface on each of its Spires and on the majority of the Central Hub. This surface is divided up into "Refugia".[16] These Refugia are as diverse as those of Earth and even of the Halos, consisting of deserts,[8] taiga forests,[9] and deciduous forests.[17] Several bodies of water are dotted around the area as well. As such, the Ark can sustain its own ecosystem, providing a variety of habitation for many kinds of life. If the Halos were fired, all forms of life could thrive and reproduce in the Ark's highly varied ecosystem, eventually being able to return to the Milky Way to recreate a full food chain on each planet. The diverse locations may also assist in the studies of the Flood in a natural, but isolated, environment.

The surface was created using Control Towers, which could change a variety of elements of a Refugia to match the conditions of a planet. This includes atmospheres, soil, vegetation, bodies of water or other liquids, and even gravity.[18]

As the Ark is outside of the galaxy, isolated in a black void of space, there are no nearby natural sources of light to power the Installation and facilitate the survival of biological organisms on its surface. To counter this problem, the Ark is equipped with an artificial structure consisting of a bright, sun-like light, with several metal arms jutting from its center.[19] From aerial pictures of the Installation, it seems the light source "scans" over certain areas to generate day/night cycles, further contributing to the growth of vegetation and controlling weather patterns.

The Foundry[]

Main article: Strip Mining Moon

The Strip Mining Moon is the open area at the heart of Installation 00, which is surrounded by a void, and is the automated factory for replacement Halo installations. This void conceals the Halo Foundry, which constructs the Halo Rings and sends them to their orbital destinations. Raw materials for the process are supplied by a planetoid roughly 1/3 the size of Earth. The moon is large enough to make several replacement installations, as seen in Halo 3 when it produced a replacement ring for Installation 04 in a matter of months.

Cooling Systems[]


A view of a cooling system.

Main article: Causeway

The intense heat generated by the Ark's Foundry, where the Halo Rings are constructed, heats the Ark up so much that multiple cooling stations are needed. At least two systems span a snowy gorge at one point or it could be that the massive cooling systems are causing this icy climate due to their nature. The systems are long, and they curve up, retreating from the Foundry of the Ark. Above the systems are small bridges, as well as two stations on each side.[20]


Main article: Silent Cartographer

Unlike other installations, there are actually multiple Cartographers on the Ark. They are updated in real time with information on the Ark's superstructure, the progress of any Halo being built and the status of any Refugia on the installation. Due to the magnitude of this information, Sentinels are more aggressive around Cartographers than normal.[21]


Main article: Citadel (Forerunner)

The Citadel is the activation site for the entire Halo Array. It sits in the Central Hub of the Ark.[8]


Main article: The Artifact
Nomis78 opened gateway

The slipspace portal leading to Installation 00.

An important component of the Ark which serves as a medium of transportation, the Artifact is a Forerunner creation which is designed to open a Slipspace portal to enable access to Installation 00.[7] The base of the portal was created from a Gargantua class ship, at the Librarian's request. This was once done to allow humanity to 'reclaim' their rightful position in the galaxy sooner.[11]

The Artifact was partially uncovered when Regret's carrier destroyed a portion of Mombasa during the Battle of Earth,[22] and completely excavated by Covenant Loyalist forces during the weeks that followed.[23]


  • There are actually two "Arks," as described in Halo: Primordium. The Lesser Ark is Installation 00, which presumably is the Ark that created all of the Halos that are 10,000 km in diameter, while the Greater Ark is the installation that more than likely created the Halo installations that are 30,000 km in diameter. 
  • In the fifth server of the Iris VMC it was stated that the Ark was built to protect humanity from the Flood and the activation of the Halos.
  • A member of HBO estimated the size of the Ark by comparing its size to a Halo installation and Earth and estimated its size to be approximately 90,000 to 100,000 kilometers in diameter.[24]
  • Six multiplayer maps are based on locations of the Ark: Construct, Isolation, Narrows, Valhalla, Epitaph and Citadel.
  • In Halo Legends, the Installation is depicted as having no land on its surface.
  • As first seen in the Halo 3 Announcement Trailer and numerous other promotional materials, the Artifact was originally thought to be the Ark itself; however, this was disproved with the release of Halo 3.




  1. 1.0 1.1 1.2 Halo 3 - Level: The Ark, Quote - 343 Guilty Spark: "Two to the eighteenth light years from galactic center, to be precise."
  2. Halo Waypoint: Ark
  3. 3.0 3.1 3.2 3.3 Halo 2 - Level: The Great Journey
  4. Halo: Primordium
  5. Halo: Combat Evolved - Level: The Maw
  6. 6.0 6.1 6.2 Halo 3 - Level: Halo
  7. 7.0 7.1 Halo 3 - Level: Floodgate
  8. 8.0 8.1 8.2 8.3 8.4 Halo 3 - Level: The Ark
  9. 9.0 9.1 9.2 Halo 3 - Level: The Covenant
  10. 10.0 10.1 10.2 Eleventh Hour, Transmission 4
  11. 11.0 11.1 Halo: Silentium
  12. Halo: Hunters in the Dark, page ??
  13. Halo Wars 2 - Collectible: Phoenix Logs - The Ark - Henry Lamb Research Post
  14. Halo Wars 2 - Level: The Signal
  15. Bungie.org - Forums
  16. Halo Wars 2 - Collectible: Phoenix Logs - The Ark - Refugia
  17. Halo 3 - Map: Isolation
  18. Halo Wars 2 - Collectible: Phoenix Logs - Forerunner - Forerunner Control Tower
  19. [1]
  20. Halo 3 - Description: Narrows, Quote "Without cooling systems such as these, excess heat from the Ark's forges would render the construct uninhabitable."
  21. Halo Wars 2 - Collectible: Phoenix Logs - The Ark - The Cartographer
  22. Halo 3: ODST - Level: Prepare To Drop
  23. Halo 3: ODST - Level: Coastal Highway
  24. [2]