Panmunjom Demarcation Line - this concrete slab divides the two Koreas; a line that has divided the peninsula and one same people for over half a century and on which each side stand two copletely opposite political ideologies.
It is not permitted to cross this line (except for when in the blue tent). It is common for soldiers from the South to glare through the window when visiors from the North come in and vice versa. There are microphones in the tents which also mark the dividing line. They record 24/7.