Zion (The Matrix)
In the The Matrix films, Zion was the last human city, which existed deep underground to hide itself from its enemies as well as for warmth. In this future Earth, the surface was too cold and dangerous for humans to live after a catalysmic war between sentient Machines and Man hundreds of years before.
Many who lived there were freed from the Matrix, a virtual computer world operated by the machines man had fought, to keep humans docile and provide electrical power from their bodies as well as computing processing power from the human brains connected to it.
In the Matrix Revolutions, considering the distance to the Machine City (that is located within the area of Southern Iraq or Saudi Arabia) and the relatively short amount of time it takes the Hammer to go to Zion and the Logos to the Machine City from the same start point; one could postulate that Zion is in fact underneath the historical Mt Zion near Jerusalem or within the vicinity of the Holy Lands. This is possible considering the timescale involved and geographic locations that the Matrix series depicts.
The Last Stand for Humanity
Zion was cylindrical in design, composed of many different levels. The Docks comprise the top level of the city, which contained ports for Zion hovercraft such as the Nebuchadnezzar as well as the city's primary defenses. The city's living quarters, temples and gathering areas comprised the middle areas. The bottom level contained vital life support machinery, such as that which supplied water to Zion's inhabitants.
Zion was lead by a Council that makes all administrative decisions. As shown in the last two movies, there were other officials that report to the Council, such as Commander Lock, supreme commander of the Zion defensive forces. The captains of the various hovercraft also had some political bearing, and their crews accompanied their captains to Council forums.
The Architect, the creator of the Matrix, used Zion as a control for the survival of the Matrix in two ways. For the first control, the Machines allowed humans who did not accept the Matrix to live outside in Zion, reducing dissent within the Matrix. For the second control, the Architect periodically destroyed Zion and its inhabitants to blackmail The One to reinsert the programming code he carried back into the Matrix. The Matrix destabilized gradually due to the side-effects of the programming provided by The Oracle. The One ostenisibly contained the 'Prime Program," the key choice-programming code needed by the Architect. Because of the Oracle's contribution, a reloading of the Matrix code was needed approximately every 100 years. After Zion's destruction, the Architect gave The One a small number of humans who were freed from the Matrix to rebuild Zion and start the cycle again.
Zion was destroyed and rebuilt five times. In the video game Enter the Matrix, the Trainman, a henchmen of the Merovingian, told the Logos captain Niobe that it took the Machines 72 hours to destroy Zion. As Neo, the 6th One, deduced in his conversation with the Architect, there were no survivors of the previously destroyed Zions that knew of the city's repeated destruction, except for the previous Ones themselves.
Despite good defense planning, Zion's defenses have never been sufficient to resist the juggernaut Machine army. The city was nearly razed a sixth time as shown in The Matrix Revolutions, but Neo saved it from destruction by creating a truce with the Machines, which stopped their attack.
Zion's defense was comprised of the hovercraft fleet, the APU Corps (Armoured Personnel Unit), and a bloc of infantry that carried plasma rifles. Unlike their hovercraft, Zion defenses do not possess an EMP device, as the use of it would not only disable any Machine attackers such as Sentinels, but the Zion defense grid and the city's APU fighters as well.
After the Truce
After large numbers of humans were freed from the Matrix (a point which marked the beginning of the online multiplayer game The Matrix Online), overpopulation became a potential problem. New recruits were sent into the tunnels on hoverbarges instead - the tunnels had become safe thanks to the new Truce with the Machines. The Zion Council also had a leader for the Zion Offensive, but that position is now obsolete with the Truce.
lt:Sionas (Matrica)