Containment
From Halopedia, the Halo wiki
Summary
Containment is a humongous level similiar to Coagulation. On each side is an old Forerunner ruin, acting each as a base. Each base, red and blue, has a large gate. About 300 feet from it, is a panel which opens each. This is used to get a vehicle inside, as you can go around through the caves, or you can jump the ledge without a vehicle. I would take the cave, however, as there are turrets seeing as far as the gates.