Zion is a fictional city in The Matrix films. It is the last human city on the planet Earth after a cataclysmic nuclear war between mankind and sentient machines, which resulted in artificial lifeforms dominating the world. It is actually a massive series of caverns deep under the ruined planet's surface, close to the planet's core, for warmth, power, and protection. Role within the franchise Zion serves as a living space for humans who have chosen to be disconnected from the Matrix and fight against the machines that created it. The city is defended by a fleet of hovercraft, an infantry force, and a corps of soldiers who operate powered battle suits. In The Matrix Reloaded, Neo learns from the Architect that the machines allowed Zion to be created as a method of coping with the problem of human choice, reducing but not eliminating the instability caused by those who rejected the Matrix. In order to prevent the entire system from crashing, the machines must periodically destroy Zion and "The One" must reboot the Matrix and choose a group of people to rebuild the city. Neo discovers that this cycle has occurred five times in the past and is about to complete its sixth repetition. In The Matrix Revolutions, the machines tunnel their way down into Zion and invade, inflicting heavy casualties as the military forces mount a defense. They retreat and leave the city in peace after Neo succeeds in stopping the renegade program Agent Smith from destroying both the Matrix and the machine world. Religious meaning Stephen Faller writes in his 2004 book Beyond the Matrix that Christianity is the most dominant religious theme in the Matrix films and that "Zion is biblically regarded as the city of God". The 2005 book Philosophers Explore the Matrix writes that "The last remaining human city, Zion, [is] synonymous in Judaism and Christianity with (the heavenly) Jerusalem". Racial matters Faller says that Zion is presented as a contrast to the Matrix, "The racial constituency of Zion is much less European and Anglo than present-day America. We are shifting the paradigm from the racially charged medium of the Matrix, where the subtext is so clearly contrasted in the extremes of black and white, to the imagined world of Zion, which is dominated by people of color." One chapter in The Matrix Trilogy: Cyberpunk Reloaded writes, "Black spirituality is evoked in the Matrix