It is the division drawn across the Korean peninsula at the end of the Korean War in 1953. Military planners in Seoul, Pyongyang, and the Pentagon all know the stats-the DMZ separating the two Koreas is 37 miles north of Seoul and 83 miles south of Pyongyang. There, one million D.P.R.K. troops face down 700,000 R.O.K. and 37,000 U.S. soldiers. It is anything but "demilitarized."On the southern side, the edge of the DMZ is a tourist attraction, a day out for visitors from Seoul. On the northern side there is, unsurprisingly, a propaganda theme park where visitors get a lesson in both American imperialism and the venality and corruption of the South Korean leaders who have kept the Korean people separated despite the ardent and heartfelt wishes of Kim Il Sung and Kim Jong Il. You know this because as you head south from Pyongyang on the Reunification Expressway to the border town of Panmunjom, you pass a gigantic billboard featuring a giant index finger and the words "One Korea."Panmunjom itself can be a disappointment. It is basically a collection of 1950s-era huts where the truce negotiations occurred. Through the middle of the huts runs a thick white chalk line-the border. It all looks innocuous enough-but step across that line and you stand a good chance of starting World War III.Of all the frequent clashes and disputes across the DMZ, the weirdest was perhaps the 1979 discovery of D.P.R.K.-built infiltration tunnels under the DMZ. Not small tunnels either-they were big enough for tanks. Still, it's not all guns and conflict. One side effect of the DMZ's existence is that the area is now an ornithologist's dream, one of the most pristine pieces of land in all of Asia-though men in camouflage with high-powered binoculars crawling through the undergrowth might not find a very warm welcome from either side.