A guide on how to get the I've seen some things... achievement on Black Ops 3.
To access the teleporter you need to turn on the power, then you need to link the teleporter to the pad in spawn. When you teleport to the Pack-a-Punch, you have to wait 30 seconds before you are teleported to one of the random locations.
There's the Office room, Samanthas' room (destroyed), Torture room and Samanthas' room (not destroyed)
Which room you will end up in is completely random, there's also a chance of not being teleported to a room at all. Best way of doing this is to keep waiting for 2 minutes every time you need to use the teleporter.