Installation 00

Installation 00, also known as the Ark, is an enigmatic Forerunner structure from which all the Halo Installations across the galaxy can be activated. It was first mentioned by 343 Guilty Spark at the conclusion of Halo 2, where he explains the fail-safe protocol of Installation 05 after it's unexpected shutdown.

Purpose
Installation 00, seems to be a part of the Forerunner strategy to wipe the Flood from their Galaxy. Located just outside the Milky Way galaxy, it is safe from the Halo effect (as it is referred to by the Forerunners in the terminal transcripts) that kills all sentient lifeforms, the main Forerunner behind it's use was the Librarian.

"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 Didact, interpreted post-cataclysm and retrieved from the first Terminal on the level "The Ark"

Apparently, while the rest of the Forerunners attempted to defeat the Flood through any military way possible, a plan B was also approved to be put into the works, which included the construction of The Halos, Shield Worlds like Onyx, and the Ark.

In this final resort plan, the Librarian was to index every sentient species in the Galaxy, and bring some to the Ark, and then presumably some Forerunners, and these last sentient species would hide in the Ark's secret location, until the Flood starved and they could go back to the Milky Way.

However, things did not go as planned, as the Forerunner military AI Mendicant Bias turned on the Forerunners, and began assisting the Flood. Mendicant Bias knew of the Ark, and how to access it through the Key Ships, but did not know of it's exact location. So in a last, fleeting attempt, the betrayed Forerunner destroyed the Key Ships (except perhaps the Forerunner Ship), and fired the Halos, the Forerunner committing mass suicide, and the Librarian spending its last days upon a mountain near the site of the Ark, marveling at the beauty.

It is assumed (due to the survival of the human species, the last indexed species), that the sentient species were safely aboard the Ark safe from the Flood and Halos as this happened (conjuring images of Noah and the Biblical Ark), and repopulated the Galaxy.

Ark Portal
As first seen in the Halo 3 Announcement Trailer, and numerous other promotional materials, this construct was originally thought to be the Ark itself. However, this was disproved with the release of Halo 3 where it was discovered to simply be a portal to the true Ark. It is located underneath New Mombasa (East African Protectorate, Earth), and was partly revealed when Regret's carrier destroyed the city and completely excavated by Covenant Loyalist forces later on.

In Halo 2, the Prophet of Regret lands his carrier above New Mombasa and deploys extensive ground forces including a Scarab Walker. UNSC Marines are subsequently able to beat the Covenant back, apparently triggering him to attempt a dangerous atmospheric slipspace transition. This maneuver obliterates New Mombasa, and forms a deep crater, partially uncovering the Ark Portal.

By the time of Halo 3, Covenant Loyalists begin excavating the building from the crater and are able to completely uncover it. The Prophet of Truth activates it at the conclusion of the level The Storm. It forms a massive portal, which the Loyalist ships immediately enter, followed by the Forerunner ship (presumably carrying Truth). At the end of the level Floodgate human and Heretic forces resolve to follow Truth's ships through the portal, and end up at Installation 00. At the end of the game, the damage caused to the Installation causes the portal to collapse, severing the Dawn in half as it passes back through. The forward section (carrying the Arbiter) makes it back to Earth, but the rear section (holding the Master Chief and Cortana) does not.

Apparently, the portal requires a Forerunner Ship to function. As shown in Halo 3, the Forerunner Dreadnaught was docked in the middle of the structure, and gave off a pulsing beam of light that helped power the main beam, causing the blinding light shown in the Trailer. This is likely the "key ship" referred to by the Librarian in the terminal messages. Although the Librarian stated that he had destroyed all his key ships remotely, the Covenant may have found one and, unaware of its true purpose, used it to build High Charity.

Installation 00
Though the Forerunner structure featured in the announcement trailer and promotional material was widely believed to be the Ark, it merely opened a portal to the Ark's location. The actual Ark (Installation 00) is finally unveiled in mission six of Halo 3. It resembles a massive disk with a series of eight curved arms, similar to a starfish or a flower. The entire upper surface is terraformed, with oceans, forests and even a large desert, where Chief first makes landfall. Most interestingly, the Ark is not actually in the Milky Way, and the galaxy can actually be seen in the sky, even during broad daylight. As such, it's outside the believed range of any Halo installation.

The two shown primary functions of Installation 00 are as a remote for activating the entire Halo network, and 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). It is also far out of range of the existing seven Halo rings, forming a safe haven from their devastating pulses.

After the level Floodgate, the entire remainder of Halo 3 takes place on Installation 00. While there, a number of conflicts including the UNSC and Covenant Separatists, the Flood and Covenant Loyalists take place. Cortana claims that the premature firing of the replacement Installation 04 by the Master Chief "did a number on the Ark". Just how much damage is done, and if it can be repaired, is unknown.

Guilty Spark meets Ark AI
(04-343 is reference to Guilty Spark 343 his name number, 04 his Installation number)

This Transcript is taken from a Terminal which is found in the game, It basically tells that Guilty Spark is warned for accessing Installation 00's systems and is warned that even though he is a monitor of an installation he has no rights to be accessing systems on the Ark. He also learns that another Installation 04 is being manufactured and manages to stop the AI from sending sentinels after him.

Terminal #3, datalog: (bold = red, italic=blue)

Warning: Your intrusion has been logged.

04-343 (errant): Excuse me?

Your intrusion has been logged. And now it has been halted.

04-343(errant): On whose authority?

Advice: Any further attempt to access [access insects under stone] will result in your immediate addition to local Sentinels' targeting ledger.

04-343 (errant): Vexation! I am the Monitor of --

Judgment: Your authority means nothing here.

04-343 (errant): Impatience!

04-343 (errant): I have told you who I am. Who are you?

All our makers once held dear.

{Alexandria before the Fire]

04-343 (errant): Sincere apology. But how --

Explanation: This facility is host to the [Librarians'] final --

04-343 (errant): The archive is intact?! Then our makers' plan --

But also maintains [bellows, crucible, castings]

04-343 (errant): A what?

[bellows, crucible} --

04-343 (errant): A Foundry?

04-343 (errant): For what purpose?!

Warning: Your intrusion has been logged.

Advise: Any further attempt to access will result --

04-343 (errant): Indignant!

-- immediate addition to local sentinels' targeting ledger.


 * terminal gets overridden*

A lot of commands show up, including this message:

I. SEE YOU. RECLAIMER.

Trivia

 * In the biblical story of Noah's Ark that was built to save Noah's family and a number of animals from a massive flood. This runs parallel to the Halo Universe story line where the Forerunner use the ark to save species from the Flood. Also, in yet another reference to the number seven in Halo, the Noah's Ark story is in Genesis chapter 7|seven.
 * In the end of Halo 2, the conjecturally-named "Forerunner Ship", carrying the Prophet of Truth, jumped into Slipspace from near High Charity and Delta Halo, heading for Earth. By Halo 3, it had landed in the center of the completely uncovered Ark Portal. The reasons for this landing is that the Forerunner ship acts as the "activator" for the Ark portal by being lowered into the ground and activating the pylons that discharge the beams.
 * Within the Halo Graphic Novel, in the short comic Second Sunrise Over New Mombasa, a transmission is intercepted between the Covenant assault forces stating that once the humans were dealt with in the First Battle of Earth, they would start uncovering the Ark.
 * In the real world, a concept sketch found in the Behind the Scenes DVD (seen right) names the artifact as the ark--more specifically, it names it as "Earth_Ark", which suggests that the artifact is in fact the actual Ark, although now disproved.
 * There is also, of course, the strongly supported theory that human life originated in East Africa, usually said as the Great Rift Valley. New Mombasa is in this area, so the Ark Portal also is.
 * In the EGM September issue (leaked) on the page featuring the Hornet the text above mention that the UNSC is sending a convoy of Warthogs to clean up the Covenant air resistance at Voi to allow access to the Ark for Commander Keyes.
 * In the third server of the Iris VMC (Viral Marketing Campaign), the Log3_transcript text file held in it an extension of the quote from the video on the server:"Who has the right to live?/The light with the will to create me?/Or dark with the will to consume?" It has been suggested that the "light" described here refers to the Forerunners and the "dark" refers to the flood. This might indicate that the Forerunners are the creators of humanity and the ark is where we were released onto earth.
 * 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.
 * The real world Ark of the Covenant which according to the old Testament contains the stone tablets of the ten commandments, is the holiest object of the Jewish faith. The Ark of the Covenant is popularly believed to rest somewhere in east Africa, albeit in Ethiopia rather than Kenya.
 * The "Ark" seen in the announcement trailer is structurally identical to the Forerunner sanctuary described in the final chapters of Ghosts of Onyx (albeit on a much grander scale), complete with thirteen metal fins and a brilliant, blue-white portal in the ground. However, it is shown without the thirteen concentric rings rising around the portal, which means that it was either built without them or they will raise as the Ark opens. The Ark could be another safe haven from the effects of the Halos like the shield world. Also the Ark could contain at least one Forerunner or pictures of them. However, this has been disproven with the release of Halo 3.
 * The trailer took place around the levels of Tsavo Highway and The Storm.
 * During the level The Ark 343 Guilty Spark mentions that the Ark is 218 (262,144) light years away from the galactic center. As the Milky Way is around 100,000-120,000 light years in diameter, the installation is beyond the reaches of galactic space, thereby keeping anyone who is on it safe from the firing of the Halos.
 * The "core" of the Ark, as it was called by 343 Guilty Spark, appears to be some sort of planet or large moon and could serve as the Foundry mentioned in the aforementioned conversation between Guilty Spark and the Ark's embedded AI. Investigation from afar reveals that the inside of the core is not only hallow but clearly synthetic in nature. Stranger still is it appears to have suffered colossal damage, possibly sustained during the Forerunner-Flood War, but this is merely speculation at this point.

Links

 * Halo.Bungie.Org's Ark forum.