Easy Pyramid Structure
From Halopedia, the Halo wiki
The Easy Pyramid Structure is a trick that can be performed in Halo: Combat Evolved, at the chapter "If I Had A Super Weapon" of the level Assault on the Control Room. It can be extremely helpful for the player in higher difficulties, when they cross the bridge at the pyramid structure.
Proceed out to the rock bridge and kill all of the Covenant troops on the bridge. If possible, try to take out the Wraith and the Elites on the canyon floor below with the Rocket Launcher from the bridge. If you cannot clear the enemies below, do not worry, just be careful with this next phase. Line yourself up with the concrete beam coming down from the Pyramid Structure. Take a step or two back, then run forward and jump toward the spine of the beam. Finally, after landing on the beam, carefully turn around and walk down the spine to the canyon floor. Be ready to take out the enemies if you did not take them out from on the bridge. You can ascend the pyramid structure with no Covenant resistance along the way until you open the first set of blast doors at the top.
You can also walk up the spine to the top of the pyramid structure for an even easier time. When the spine gets thinner, look down, there is a V-shaped niche leading down the wall. You can slide down this to get to the top level of the pyramid without taking any damage.