HIGHCOM Facility Bravo-6
From Halopedia, the Halo wiki
Facility Bravo-6 is the official name for the massive base the UNSC High Command (HIGHCOM) has located in Sydney, Australia. Below the HighCom Bravo-6 Facility is another massive facility called "The Hive". It is three-kilometers below the surface and reinforced with massive blast plating, anti-EMP armor, and three-kilometers of solid rock. The UNSC Security Committee meets here. After The Battle of Reach, it is assumed to be the headquarters of the HIGHCOM.