The game board is built from hexagonal Sector tiles during the game. Each Sector represents a star system and may contain Population Squares representing worlds Producing Resources. There are three Sector Rings: Inner (I), Middle (II) and Outer (III). Each Sector’s corresponding Ring is shown by the Roman numeral on its tile back. At the beginning of the game, only the Galactic Center Sector, Guardian Sector(s), and players' Starting Sectors are placed on the table; the rest are placed in the empty Zones of each Ring during the game (see the Placing Explored Sectors section of the Action Phase section for details on Sector Placement).