Installation 04 is a fictional location in the Halo video game series, specifically featured in Halo: Combat Evolved. It is a massive ringworld, part of the Halo array, designed by the ancient race known as the Forerunners. The installation serves as a weapon against the parasitic Flood and is a key setting for the game's events. The player, as Master Chief, explores Installation 04 while battling the Covenant and the Flood. The environment includes diverse landscapes, such as forests and structures, showcasing advanced technology. The installation plays a crucial role in the overarching narrative of the Halo franchise.