W.A.S.P. in Part 6 (Sopot's Citadel)
The first autosave point after crashing the tank through the Citadel wall is the start point for this. When you open the door, you'll have to kill three soldiers (two on the ground and one up on a parapet). After you kill them, look near the fence to the left of the door you just came through. On the ground is a square plate. Destroy it with an explosive (hand grenade, time bomb, grenade shot, rocket) and climb down the hole. Turn on your nightvision and head down the tunnel. Blast a hole in the wall around the second corner. Destroy the boards on the floor and then drop down the hole. Duck down and squat-walk to the next ledge. Jump up and head down the hexagonal tunnel that turns right.
There are three soldiers on the platform above you. One well-placed grenade will kill all of them at once. Jump over the pipe and climb the ladder. On the opposite wall are two launchers and several EMP grenades.
At this point, you can proceed out the double doors into the central courtyard, or retrace your path and enter the courtyard the normal way.
Added by: Ichigo Kurosaki Dec 18th 2008, ID#8696