From Halopedia, the Halo wiki
Elysium City is an urban center located on the planet Eridanus II.
In 2513, M-EDF 9/21/1, commanded by Lieutenant Colonel Ponder, had an operation in Elysium City. M-EDF 9/21/1 was ordered by FLEETCOM to neutralize the second-in-command to the Insurrectionist leader, Colonel Robert Watts. Against FLEETCOM's insistence on a show of force, Ponder attempted to personally speak to family members of the second-in-command, when a M-EDF 9/21/1 sharpshooter took a hasty shot, completely collapsing the situation.
Elysium City was also the city in which John-117 grew up, before he was chosen for the Spartan-II project and replaced with a flash clone. John originally attended school at Elysium City Primary Education Facility No. 119, where he met both Dr. Halsey and Jacob Keyes in 2517. The school had a substantial playground, including Gravball courts, and a grassy hill were John-117 played King of the Hill.
In 2525, an insurrectionist attack on a nightclub resulted in the deaths of a number of innocent civilians as well as one Colonial Military Administration pilot, sending another into a coma. The resulting investigation into poor management and guarding of military equipment on the CMA's part would be one of the causes of the organization's downfall.
List of appearances