Location: It's outside in a caged room, clearly visible, but surrounded by invisible walls where even high jumping zombies cannot get in.
Description: It is a 1-way entrance teleport spot to a caged room. This cage has 2 vending machines provided, very easy to set up. All you need to do is shoot 1 vending machine downward onto the teleport spot, and one right behind to for support. To get to it, it's a secret, but fairly easy secret to get to.
Pics & Demo is provided below.
On the demo, at 45K you can clearly see that even 1 vending machine can hold them off, but 2 set up is not that hard, and pretty much impossible to get through. Watch in peter's perspective, as it's an easy set up, and easy win.