I used to work in a high security place where we not only had to wear our ID badges all the time, but entry and exit was by way of a "mantrap", a small sealed room that had two doors, one at either end, and only one door could be opened at a time. You walk into the mantrap, close the door you just entered, it locks automatically, then the other door gets unlocked manually after an inspection via video link by those already inside the building, and you can then exit the mantrap and go into the building proper. The part of the building that I worked in was an underground bunker arrangement. Fun times!