High Ground vacation
From Halopedia, the Halo wiki
Method 1
(You need to be on Forge to do this, and have at least two players.)
To get out of High Ground Player 2 must get into a Mongoose side seater. Player 1 then turns into Forge mode and picks up the Mongoose (You HAVE to be in side seater to do this, or you will climb out). Player 1 then pushes it behind the rocks on the left (if they are facing towards the sea) and Player 2 climbs out. Then Player 2 turns into forge mode and can climb up to the edges of the map. *Note* It is easyer to do this glitch if u overload the map
Method 2
Spawn a teleporter outside of the map, and spawn a second one out on the map. This way can be easier if you don't understand the first method.