Der Reise Easter Eggs....
this is pretty fun to do...
* To find the musical Easter egg you need to press use on the 3 green glowing jars that appear to have spines in them. 2 of the jars are (when facing away from the pack a punch machine) in the room to the left through the first door by one of the mystery box's respawn, and the third and final one is in the factory room where Teleporter B is located, in a side room. The song that plays is Beauty of Annihilation.
There are three audio clips that i have found located around the map, one in the form of a walkie talkie, the other two in the form of small boxes. To activate the audio on them you go up to them and press square(ps3) presumably the same button (left one) on the xbox 360. The first is found in the main room where you respawn/start, go to the right of the stairs going down, it is standing next to the barrels, lie down and activate it. The second is located in the teleporter room at the very end of the map where there is the balcony, this time it is a box that is located on the shelves of the cabinet at the bottom of the stairs leading to the balcony, once again press square. The third i found is located in the room joined with the doubletap room and has the bridge going over to the teleporter. Once again it is a box, it is found between the metal cabinets in the top left of the room (on the left before you go over the small bridge to the teleporter), once again press square. THeres aslo one which is behind the boards on the underground section of teleporter c, at the end of the tunnel, this one gives hints at a possible new map pack. These audio clips give us an insight to what happened at the factory before it became overrun with zombies. There may be more so look out for anything unusual and press square.
* Near teleporter B, if you go onto the balcony, in the destroyed building across the street you can see the legs of a hanging person(similar to hanging people on previous two maps). If shot, feathers seem to come out.
* There is a readable message inside an Air Conditioning unit on the lower side of the bridge that lowers with the power. It is viewable by looking through a crack in the unit with a PTRS's scope. It reads: "In the event of any critical failure, you are instructed to take your cyanide tablet that's included in your field operations kit. In the event that you have misplaced yours, there are several methods that will accomplish the same task. For example, the best (end of page.)
* Another book can be seen outside of the map. It appears to have the page prior to this page. It reads: "It is the responsibility of absolute secrecy. No one is to know what you do, where you work, our research has uncovered, or what our purpose will be. You will have no further contact with your governments, or with your families. Your decision to fully dedicate your lives to Group 935 is absolute. Attached is your field operations manual which will direct you should our mission get compromised. We cannot afford to let this power fall into the wrong hands, and therefore the field operations manual should be considered your bible. Make your preparations now. A new dawn is beginning for mankind. Dr. L. Maxis"
* In addition to this message, there are several messages written on the walls that you can clearly see.
* In the alleyway on the right (facing away from the pack a punch machine) there is a distinct shadow of an upright teddy bear on the wall.
* In the starting area if you look down one of the drains to the left of the stairs you can find a note with random symbols on it.
* If you throw a Monkey Bomb into the furnace, it will start to scream. After it explodes, you hear a little girl (probably Samantha) say "Why are you so cruel to Mr. Monkey? Mr. Monkey just wanted to PLAY!!!."
* If you open the door to your right from where you spawn, by the Double-Barreled Shotgun, if you look down, you should see some wood panels. A few panels will be broken and inside there is a note. It's a little long, so you might want to have 2 or 3 people covering you while you read it. The message reads: "...is produced by bombarding an Americium-243 nucleus with a Calcium 48 nucleus. It then decays (writing is blurred)... after further decay a meta-stable isatope is formed. This leads us to believe that transference of matter is indeed possible, and even the re-animantion of b... (faded, but it is presumed to be brains)"
* Written near the doors leading to the teleporters on the walls is a message reading "Return Through Aether"
* The room with the Quick Revive has a sign at the entrance that says "L. Maxis, MD Office" showing that that room was Dr. Maxis's office and might have been the head scientist.
* On the roofs of some buildings, the words "help" and "SOS" or "505" are visible. They seem to be formed from sand bags and planks.