In Halo 3, how do you open the gate in higher ground?

[summer-is-hot]

i blasted it with everything and it won't open! i am playing on assualt and i edited the map with forge. ive tried playing it on forge and custom games
i'm talking about in multiplayer!

 

[sarin]

I think the oracle opens it.

 

[Ryoma Echizen]

Use the MAC guns...take 'em out.

 

[Asim Mehta]

There is a switch to opening it. It is somewhere in the structures around that gate. Duhhhh!!!!!