Or...you can try this hard way, which I did awhile back...(need to use a trainer)
1. Change a gun's projectiles to Banshees
2. Make your way to the very end of the level
3. Go down the elevator, and enter the bomb room
4. Look left and you'll see the mac gun being loaded
5. Hop onto the middle section where the sliding structure COMES BACK to the small rounded corner
6. Hop inside this corner
7. The sliding structure will come back, and "squish" you through the corner and down below. You'll fall, but land on something hard(the ceiling of the room). Now, shoot your weapon that has the Banshee projs
8. *Hard Part* Try to find and get inside a banshee. When inside, fly up a little to see the room. A couple parts of the room aren't solid, so find one and fall into the room.
Note: If you fall down too far(to the very bottom of the level) don't worry, just shoot out a banshee and make your way back up.
Here's a video I made awhile back(shows me inside the room; not doing the steps above)...
http://www.putfile.com/media.php?n=ICCsm
or
http://x4.putfile.com/videos/a7-6201024077.wmv (which is a direct link for those, like me, who have slower connections...and/or would rather save it)
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Hack0r told me this... now my question is solved, and i hope you guys will get the chance of getting in there too!