From Halopedia, the Halo wiki
Zenith, also known as Zenith Anniversary, is a multiplayer map in Halo 2: Anniversary. It is a remake of Ascension from Halo 2, with some minor changes. Ascension is one of the seven Halo 2 multiplayer maps that have been completely re-imagined in Halo 2: Anniversary.
Zenith is set on and around a relay station, a Forerunner communication structure vital to the upkeep of Halo installations. This particular site, unlike prior sites observed, is placed at high altitude above the surface of Delta Halo and kept in place using gravitic control systems. The site, like other elevated relays, utilises its own slipspace translocation system for travel to and from the Delta Halo surface.
Changes from Ascension to Zenith
The following achievements can be unlocked on Zenith on Halo: The Master Chief Collection.