Do not leave Seoul without taking a day tour to one of the weirdest and scariest spots on the planet – the DMZ (The Demilitarized Zone) on the border between North and South Korea. Two armies have glared at each other across the DMZ for more than 50 years, ever since the end of the Korean War in 1953.

Established on the ceasefire line at the end of the Korean War in 1953, this is where negotiations between North and South took place. Only an armistice was signed at the end of the war, not a full peace treaty.

The 4km-wide DMZ scars the land from coast to coast and divides the Korean Peninsula into two antagonistic countries. It is probably the most heavily fortified border in the world - high fences topped with barbed wire, watchtowers, an antitank wall and obstacles. Thousands of landmines line both sides of the DMZ. Seeing the military build-up on both sides, a visit here is a sobering experience.

Access to Panmunjeom, the  "truce" village that straddles the border between North Korea and South Korea, is only for tour groups and you must carry your passport and follow a strict dress code - no offensive T-shirts, ripped shorts, flip-flops or miniskirts.

The tour includes visiting one of the small, blue UN buildings that straddle the border and look like temporary classrooms. Inside are simple tables and chairs. Walk to the far end and step into North Korean territory - a strange feeling. North Korean soldiers used to peer in the windows, but recently they have kept watch from a distance. On the South Korean side soldiers in sunglasses strike taekwondo poses - partly to intimidate the North Koreans and partly to provide a photo opportunity for the tourists. Welcome to showtime, DMZ-style.

The Monastery Visitors Centre sells DMZ baseball caps, T-shirts and other souvenirs. Nearby is the world's most dangerous golf course, with just one 192-yard, par three holes surrounded by barbed wire and landmines. The bunkers here are made of concrete rather than sand.

A highlight is the walk along 265m of the 73m-deep Third Tunnel of Aggression. The third such tunnel, found under the DMZ, was dug by the North Koreans so that their army could quickly march through and launch a surprise attack on Seoul. Coal was smeared on the walls and when it was discovered in 1978, the North Korean authorities claimed it was a coal mine!

Most of the DMZ has been sealed off to all people for more than 50 years, and ironically, this has made it an ecological paradise, encouraging wildlife such as Manchurian cranes, whooper cranes and white herons, as well as rare plants. Environmentalists hope that when the two Koreas eventually cease hostilities, the DMZ will be preserved as an official nature reserve and memorial to the nation's period of division.

The article 'Seoul’s Demilitarized Zone' was published in partnership with Lonely Planet.