There is more to this place than meets the eye...
Cairo Station, or The Palace of His Almighty All-Powerful Glorious Excellency Hood, is a log floating above Earth. Grandmaster Hood resided here during the whole duration of the Human-Covenant War, despite the fact that he was the Leader of all UNSC forces.
Lord Hood likes to sit here all day and give orders to people while drinking his favourite Shiraz Wine. He even has his own private entertainment room fitted for when he gets bored. In fact, Cairo Station is secretly a hotspot for League bigshots during their time off work. Beneath the surface is an armada of clubs and bars, widely regarded as some of the best in the Galaxy. Hoody resides over this Empire, and it is where he secretly gets all his funding for the upkeep of The League's Navy.
Cairo Station also houses one of the only known Terrantime farms. Lord Hood enjoys these citrus snacks and doesn't let anyone else eat them, even though they're the only food allowed on the whole station apart from in the Cantinas.