Crouch and go on to stealthily kill the armored dogs that are past the bridge. You can do this by getting close to them while crouching. Once you've done that, be very careful about this next area. There are 4 super soldiers patrolling this hallway. To the very left of the hallway entrance is some armor that you should pick up, as it gives you enough armor to have max armor. You'll want to disable the first super soldier by the power generator before destroying any of the other ones. Once you've done that, destroy the one patrolling the area next to you and wait a while. Continue down the hallway and disable/destroy the next super soldier by the power generator. There is one last super soldier left that is patrolling the second to last power generator. Once you've taken him out, there is some health to the very left of the next electrocuted door.
To the left of the area after this door you can climb some pipes to get some 25 armor. Climb down the stairs and then climb up the rubble on the wall. Go through the vents until you can go left or right. Go right and pick up the Gold piece. This is the first gold piece of the game, and you can collect 64 in total. Continue down the left path. Before dropping down into the room below you, be warned that there are two super soldiers in this area. The best way to deal with them is to drop down, destroy the wooden boxes and take the machinegun that is located there, and destroy them with it. However, in the left side of the room, there is also two electric stands, which you can use to turn them off.
You can then go through the electrocuted door up ahead. There is also a wooden box with some health to the left of the door if you want it. Continue through the door, crouch, and head as straight as you can until you reach a hallway. In this hallway is a super soldier, so be careful. Look in the right corner of the hallway from where you are now, and you will find another Gold piece. Go back just outside of the hallway, and follow the hallway along the balcony. Be sure to be crouched, as there is an armored dog in the last hole connecting the balcony to the hallway. Watching out for the super soldier, head through the small opening across from the balcony, and then run all the way over until you reach the electrocuted door. Watch out for the super soldier again, as he can shoot you through the gate.
Up ahead will be a disabled super soldier with his cord still attached. Get rid of the cord and then go behind the elevator to turn on the power. It is advised you take the super soldier's machinegun and throw it onto the elevator. Go down and then you will end up in a hallway with two super soldiers. Kill both of them with the machinegun you picked up earlier. Once they're dead, go back to the elevator and head to the gate area on the left. Destroy the boxes for some health if you need it. To the very right of the boxes will be a climbable wall, with a Gold piece in one of the windows to the left.
Continue through the hallway and go through the electrocuted door. Go through the next door and then climb up the rubble. Go through the vents and then wait for the armored dogs to turn away from the direction you're facing, and crawl into the small vent to the left. Kill the armored dog located inside. There will be a vent that you can open and drop down. There are also two more located in this area that lead to the same sewage area, but you do not need to go through them.
Continue down the path until you can either turn left or continue straight into the sewers on the other side. Continue straight and head to the end of the path, and there will be a Gold piece on the ground. Now head back and continue down the other path. In the left part of this area there is a breakable wall you can destroy with your pipes. Then climb up the wall to reach another sewage area, and then another climbable wall. Go up it and kill the armored dog that is located above it. To the right there is a vent you can use to get to the main jail area. Kill the dog that lies in front of the vent straight ahead. Go through that vent and you will find yourself in a jail that contains another Gold piece. Exit the jail and then head towards the final armored dog in the area. Kill it, and then enter the vent it was guarding. Go up the ladder and you will find yourself in an area with a super soldier. To the right of the entrance you came through, you will find the electricity panel you can use to disable him. Follow the path until you can bring down a vent opening, climb through it, and head through the vents until you fall into the Sanitarium.
Continue down the left path until you come to a door that you can interact with. Intreact with it and then run and crouch at the same time to go through it. From here, go to the room to the right that has a blood trail leading to it. Open the hole in the room, and fall down onto the bunk bed. If you look at the first be, then you will be able to access the second Nightmare Level. Continue until you see Wesley being taken by Rudi. Go through the door and then attack the Nazi who tries to kill you. Climb up the vent and hide behind the breakable box. There will be a large mechanical dog the is going to patrol the Sanitarium. Wait for him to go through the main gate, then run to the door on the left side of this jail area that you can open and slide through. Go up to the next floor, and then run across to the other side of the balcony area and open the vent. Be quick about this because the mechanical dog will try and hit you otherwise. Go through the vent and once you fall down into the next vent, go back the direction you came from. There will be some health, armor, and a Gold piece.
Continue down the path and you'll eventually come across the first commander of the game. These enemies will spawn more and more Nazis if you come into their vision or hit them without killing them. As long as there are nazis and commanders, nazis will trigger the alarm as well. The best way to go around this is to kill them before they can see you using the Handgun with the silencer. You can kill the first one by doing a sneak attack from behind. Then, jump to the very right into the water below you. Swim to the left area until you see some stairs. Crouch down, and be on the lookout for a Nazi that is patrolling the area up ahead. You can kill him without alerting any guards by shooting him in the head twice. Go towards the second floor stairs up ahead, but be careful, there is a nazi patrolling the top area. Shoot him in the head twice and he'll be dead. Crouch and slowly move up on the last commander, killing him by shooting him in the head once.
Before you pull the lever next to the second commander, there are some things you might want to do first. If you backtrack the area past the stairs where you came up through the water, you will eventually come across two breakable boxes that lead into a vent area. This vent area contains a Gold piece. If you backtrack even farther, there are another two Nazis patrolling the area so be careful, but there are ammunition, health, and armor in that area. Go back to the lever next to the second commander, and then continue past to the other side of the bridge. There will be some armor as well as another Gold piece.
Now you can pull the lever. Once you do, there will be several swarms of nazis that come to try and kill you. However, you can use the pillars in the area near the last gold piece as cover. Once all of the nazis are dead, you can go into the boat and start it up. Once you begin travelling, be sure to get a hold of the machinegun. There will be two flying sentries that will shoot missiles at you that need to be taken down fast. As you go through the waterways, there will also be more nazis and a few more sentries along the way. Near the nazis will be explosive barrels that are really effective at getting rid of them. Once you've reached the next gateway, get out of the ship and pull the lever. Once the cutscene is over, the next gate is unlocked, and you will now be starting Chapter 2 - Docks.
