Had to check for unknown WiFi signals for a client. So I was walking around with my laptop in hand and a WiFi antenna. So cafeteria, toilet, staircase, server room, chill out lounge, parking spot and rooftop. It was pretty funny trying to assign all the WiFi networks to the cars in the parking lot and to the other buildings and stores around. That day I learned just how far away you can still see WiFi networks if you use a reasonably strong antenna (just a usb-stick basically).