BERLIN It was once one of the world's most deadly frontiers but has since been converted into one of the planet's most fascinating bicycle paths -- a green belt that offers a surreal ride into Berlin history.
The "Berliner Mauerweg" (Berlin Wall Trail) follows the wall's 160-km (100-mile) route and the accompanying "death strip" that encircled West Berlin during the dark decades of the Cold War.
At least 136 people were killed trying to get through the Wall that divided Berlin from the day it was built 50 years ago on August 13, 1961, to its fall on November 9, 1989. Most were shot by East German border guards. About 5,000 made it.
In the euphoria that followed the despised Wall's collapse, most of it was quickly destroyed and early proposals to preserve at least a few pieces for posterity or turn the "death strip" into a bike trail were dismissed as madness.
"Those who forget the past are condemned to repeat it," said Michael Cramer, a Greens party leader who ignored the widespread criticism and spent a lonely decade pushing to get the Berlin Wall Trail built.
"Everyone wanted the Wall gone as soon as possible and they called some of us in the Greens who wanted to preserve parts of it crazy," Cramer told Reuters. "Unfortunately, there was a certain Prussian thoroughness in demolishing it all."
The city council finally got behind his project in 2001, agreeing it made sense for a city with financial woes to develop its top tourist attraction. The trail is now used daily by tens of thousands of people.
FEARS OF ANOTHER WAR
"It took 10 years but it was worth it," said Cramer, 62, a physical education and music teacher in West Berlin for two decades before switching to politics and now a member of the European parliament.
"There was a realisation that you can't eradicate history. They realised it wasn't just tourists asking 'Where's the Wall?' but people in Berlin too."
Cramer was a 12-year-old boy when the Berlin Wall was built and remembered being terrified by the possibility the tensions around the construction would lead to another World War.
"I cried when I read the Wall was being built," he said. "I always thought we'd never have a war like my father and uncles went through. But suddenly a war loomed. I've never forgot that feeling and the Wall fascinated me from that moment on.
The Wall turned into an obsession and he often rode the perimeter of the west side.
"The first time I rode along the Wall after it opened, I was able to cross back and forth from east to west and was amazed to think just a few months before I'd have been shot to death for trying to do that," he added. "It was an incredible experience."
"TRYING TO FLEE"
The Wall complex that split East and West Berlin as well as sealed off West Berlin from East Germany was between five and 500 meters wide. There were a series of barriers, minefields and barbed wire to keep East Germans far away from the Wall. Much of the western side of the Wall was covered with graffiti.
It was built to stop a flood of East Germans to the West -- some three million left from 1949 to 1961. About 3,200 people were arrested for trying to cross after the wall was built, jailed for "Republikflucht", or trying to flee.
The trail that now stands in the Wall's place was at first fairly primitive, poorly marked and much of it on the cement slabs used by East German border guard patrols but also on sandy terrain where bicycles had to be pushed.
Over the years, a total of 10 million euros has been invested on upgrading the bike path and now almost all if it is paved or on well-maintained dirt trails. About 900 grey and white signs now mark the path, all at a height of exactly 3.6 meters, the same height as the Wall in 1989.
Whether walking their dogs or pushing baby carriages, going for jogs or commuting to work, many people have made the Wall Trail an integral part of their lives.
PEDALING ALONG THE "DEATH STRIP"
In summer months, flocks of cyclists can be seen pedalling along the trail, especially along the 43 km (27 miles) of the "death strip" that snaked its way through the inner city.
Some hardy souls venture around the entire length of the trial in a day or two, and on August 20 a group of marathoners will run the distance in a race expected to last about 30 hours.
It is a remarkably pleasant journey and at the same time a fascinating trip back to a horrific period of history.
Scores of signs posted along the route detail historical landmarks, especially poignant escape attempts and some of the heartbreaking stories of those who failed.
"This is the spot where 20-year-old Chris Gueffroy was killed on February 5, 1989. He was the last victim shot dead while trying to escape from East Germany," reads one.
"Peter Fechter, 1944-1962...he just wanted to be free," reads another, a memorial to an 18-year-old bricklayer was shot by East German border guards and left to bleed to death in the shadow of the Wall. His unanswered cries for help were heard on both sides of the Wall.
New houses have sprung up on parts of the former death strip and horse stables and chicken farms have been established on the reclaimed land once patrolled by menacing East German border guards and watchdogs.
"The trail is to help Berlin come to terms with the past," says Cramer. "It's a reminder of not only of the division but also of how the Wall was peacefully swept away in 1989."
(Editing by Sonya Hepinstall)