In Assassin's Creed Odyssey, the ruined city of Mycenae represents Mycenaean Greece.
Mycenae was a major fortified center of the Mycenaean civilization, which flourished on mainland Greece during the Late Bronze Age. Its famous archaeological remains include massive stone walls, monumental tombs, and the Lion Gate. The historical Mycenaean period ended centuries before Odyssey's main setting in the fifth century BCE.
Odyssey includes Mycenae as an archaeological location that players can explore in the Argolis region. The game's world combines contemporary classical-Greek settlements with older ruins and sites tied to earlier civilizations.
Mycenaean Greece is not the same as Minoan Crete. The Minoans were centered on Crete, especially at Knossos, while the Mycenaeans were based largely on mainland Greece. Both cultures are important to Greek prehistory, but the ruins at Mycenae specifically belong to the Mycenaean civilization.