During a 1993 visit to Korea, US President Bill Clinton described the North Korea - South Korea border as the scariest place on Earth.

It is the world’s last Cold War frontier, and has separated the 2 Koreas since 1953.
The division between North and South Korea has been described as wider than the German division ever was.
It is 151 miles long and is the most heavily fortified border in the world.
There is a 4-kilometer-wide demilitarized zone (DMZ).
The Military Demarcation Line (MDL), also known as the Armistice Line, or Ceasefire Line, runs along the middle of the DMZ zone. It runs near the 38th parallel.
US and South Korean soldiers patrol this line along the South Korean side while North Korea People’s Army (NPKA) patrol along the North Korean side.
Frequent skirmishes have occured along the line over the years. At the Joint Security Area (JSA), the only place along the border where North and South military forces see each other face to face, over 750 overt acts of violence has been recorded since 1953. In addition, countless fistfights, shouting matches, exchanges of rude gestures, and other provocations have also occurred.
Tour groups are allowed inside the DMZ only with heavy military escort. A blogger reported that photography is not allowed in most areas of the border, therefore pictures are usually taken quickly & discreetly without the usual time taken preparing for things like picture composition. Some has to be taken with the camera still strapped to one’s shoulder or dangling from one’s neck; just pointing the camera in a particular direction and taking a photo without being able to peer through the viewfinder, hoping the picture will turn out ok, and all the while pretending not to do anything one’s not supposed to.
A North Korean soldier looks at passing US patrol on the South Korean side:

From oldbluejacket.com, here are some photos and descriptions of the DMZ at Panmunjom, taken in 1977.
This is the room where all the negotiations with North Korea take place. Half the room is on the South Korea side and half on the North Korea side. The border runs right down the center of the green table in the foreground - I’m actually standing on the North Korea side when taking this photo.

The Korean border is the cement line on the ground just behind the friendly border guard in the foreground. The guards in the background are North Koreans who were filming our tour group for some unknown reason. The 2-story building in the far back- ground is a facade, it is only about 10-15 feet deep, it was built for show and propaganda purposes.

Site of the 1976 poplar tree incident - - Two US soldiers, sent to clear a tree that obstructed the view in the Panmunjom truce zone (the tree to the right of the check point station), were hacked to death by a North Korean soldier.

The following image is from theodoresworld.net. On the left of the cement line is South Korea, on the right is North Korea. (more…)