Well, its kinda hard to explain. But youll eventually come to a room that loops around in a square. I belive that you get to it after you climb some steps. And in that squareish room youll see a mound of dirt, then you know youre in the right spot. Kill all the fuckheads and look for a doorway that leads to a very small room, theres a ladder in there. And I think its up there. I may be completly wrong. Its a been a while since Ive actaully been able to make it there without modding my game to hell. >.
much like bando said in his post when you go up the stairs (actually a ladder) make a right you will see a door go up to the door and hit "F" to decode the door,it will take bout 25 seconds in the mean time some monolith NPC's will spawn for you to fight when the door opens make a mad rush to it..make sure you save the game when you reach the door this way if the monolith NPC's manage to kill ya you can always reload the game back to that spot