Elysium City
From Halopedia, the Halo wiki
Elysium city was the city in which Spartan-117 (Master Chief) grew up, before he was chosen for the Spartan-II project and replaced with a flash-clone.
Very little is known about the city itself, or Master Cheif's past in the city, but Elysium has strong links with the trends of the Halo series, especially through it's name. Elysium was a greek word to describe a paradise, where Hero's and warriors went after death. It can be likened to the modern conception of heavan.