From Halopedia, the Halo wiki
Asylum is a map variant of Forge World. It is a remake of Sanctuary from Halo 2, built into the Quarry. Asylum is featured in the Rumble Pit, Living Dead, Team Slayer, Team Objective, Multi Team, Doubles Arena, and Team Arena playlists.
Players used to be able to camp on top of a rocky wall via sprinting and jumping. It appears that Bungie added a soft kill zone there to prevent players from gaining an unfair advantage.