That's where the civi hog is, true. However, you can't reach it from that way.
First, you need a banshee. Now, fly up to the very top (the light at the top). Now, go in reverse up through the hole and land on a corner. I'm not sure which one it is, but when you look down, you should be able to see one of the arrows pointing to the base. That arrow will be pointing foward from your perspective.
Exit the banshee and hug the wall. It should teleport you to the room with the civi hog
omg man bad sweet good 1000000000000000000000000/10
ps i dont usaly post for stuff but this was too ausem to not say nothing thank you lightling your my best freind
Lol, people who 'say' they found the yellow civie hog on Halo 2 said the horn was an elite going wort. Maybe for your hog have it as that? Im not bothered about the horn much though...