It's heavy action from the start. Shoot the guards, grab the ammo, then deal with the SS. Now you have a machine gun.

You will be attacked from every possible angle on your way to the Silver Key found behind the pushwall and the column in the south-eastern corner of the floor. A 1-up is found in the room in the south-western corner. In the secret room not far from the entrance is another set of pushwalls that let you pass through the wooden barrels in the central hallway. Prepare for a hard fight getting into the main eastern section, the Gold Key is found in one of the northern rooms of this area. Then you make it for the elevator.