Siwa is the ancient Egyptian city and oasis where Bayek's journey begins in Assassin's Creed Origins.
Bayek is a Medjay from Siwa, and the opening sequence establishes his role as a protector of the community. His investigation begins there before the story expands across Ptolemaic Egypt. The remote oasis gives the game a smaller starting environment before Bayek reaches larger political and cultural centers.
Origins later takes players to Alexandria, Memphis, Cyrene, Giza, and many other regions. Alexandria is particularly important because it is a major intellectual and political center, but it is not Bayek's birthplace or the starting location of his journey. Siwa remains tied to Bayek's identity throughout the story.
The game is set in the first century BCE, during the reign of Cleopatra VII and the Roman intervention in Egypt. It depicts the formation of the Hidden Ones, the organization that becomes the historical precursor to the Assassin Brotherhood.