oooh a second pile of rocks? No I have not. I've only blow up the 1st pile that leads down a downward path to the elevator.
Where is this second pile of rocks? much appreciated

Edit: I just figured it out! Thanks. I knew that section was a bit unsual. Thanks heaps. Been slaving over this for hours.
Double Edit: That key doesn't open the 1st floor door though

That key just unlocks a random chest.
How am I suppose to find the mute goblin? (As part of the main quest)