Zone 67
From Halopedia, the Halo wiki
Zone 67 was a highly classified area on planet Onyx. After the UNSC expiditions uncovered Forerunner artifacts, the Office of Naval Intelligence took over, creating the zone for excavation of any forerunner artifacts and technology. Zone 67 was the location of an ONI base, supporting a compliment of troops and an Artificial Intelligence. It also housed a Slipspace COM Launcher, one of only three known launchers in the galaxy.
After Camp Currahee was constructed to the south in 2531, a team of Spartan-IIIs from Alpha Company went missing in Zone 67. ONI cordoned off the area, ensuring that in the future, no more Spartans would go there.
In 2552, after The Battle of Installation 05, Zone 67 turned active, with huge numbers of Sentinels coming out of the area and destroying the excavation team, eventually attacking Camp Currahee as well. The Sentinels then continued to excavate Zone 67 during The Battle of Onyx. The planet eventually exploded, destroying Zone 67 but keeping the Forerunner ruins inside it intact.
