From Halopedia, the Halo wiki
The coral highlands was a primeval area of the Forerunner constructed Shield world of Genesis. The coral highlands is where the Gateway sat, in order to mask its strong energy output with the excessive bio-readings of the area.
Geography and ecology
Fractal plants, paddle grass, fiber optic succulents, aloe husks, floating lotuses, barrens, and warbled fans are all seen throughout the region. Lumenon and logrodites also primarily live in the coral highlands.
During the Battle of Genesis in October 2558, the Guardian Custode originally from Meridian arrived and deposited Blue Team in this region. Blue Team would fight off Jul 'Mdama's Covenant, Prometheans, and the Warden Eternal himself.
List of appearances