Panmunjeom, UN Joint Security Area

South Korean soldiers (in the foreground) spend their day staring northwards at the somewhat more relaxed North Korean soldiers (there's one at the left of the three doors at the top of the stairs).

This is well inside the DMZ separating the two Koreas, and is the only place where the two sides meet face to face.  There have been numerous hostile incidents including defections and firefights at this very location.  The dotted line itself is at the midpoint of the blue conference rooms.  Amazingly, these hostile forces commingle inside the conference buildings, not observing the border.