Hidden gargoyle

Finding It
On the Halo 2 multiplayer map Backwash, go towards one of the extending Forerunner bridges. Find a plant that looks like you can walk on it. Crouch jump onto it and walk up it. Turn around and you jump forward. Walk toward the wall and then jump to the other side of the bridge and you will see a gargoyle. You can jump onto the gargoyle, but it's not solid so you will go through it.

If you carefully jump on a ledge behind the gargoyle, the Monitor will stop moving.