Along the 100-mile path of the old Berlin Wall, more than 300 ultramarathon runners will start a gruelling race on Saturday.
A quarter-century after it fell in the heady days that brought down communism. Extreme athletes from around the world will join the third event of its kind in the German capital, which will also be a historical pilgrimage along the symbol of the Cold War.
"I was astonished by the size and length of the Wall and the places it passed," said the oldest registered participant, Sigrid Eichner, 73, of the 160-kilometre stretch.
The Berlin woman, who has lived in the city's east since 1974, is a legendary veteran of more than 1,800 running races around the world equal to or longer than the 42.195-kilometre marathon format.
For Eichner, the daunting quality of the Berlin race echoes that of the "anti-fascist protective wall" which the former communist East Germany started building on August 13, 1961.
Designed to stop an exodus of people to the West, it cut through city blocks, neighbourhoods, fields and forests and was shadowed by a heavily mined "death strip", overlooked by watch towers and patrolled by soldiers and dogs.
Today the path of the Wall is a hiking and cycling trail, which takes a seasoned ultramarathon runner 16 to 30 hours to complete, depending in part on the weather. Weekend forecasts are for summer showers and temperatures up to 20 degrees C (68 degrees F).
Promoted as a marriage of "sport and history", the ultramarathon, like previous editions in 2011 and 2013, will be dedicated to one of the "victims of the Wall" who paid with their lives trying to escape.
Each runner who makes the full distance will receive a medal with the image of Peter Fechter, who was 18-years-old when he was shot dead by border guards during a 1962 escape attempt near the well-known border crossing Checkpoint Charlie.
- 'Running with our heads' -
The race, called "100MeilenBerlin" (100MilesBerlin), starts at 0400 GMT in Prenzlauer Berg, which since Germany's 1990 reunification has been transformed from an East Berlin working class district into a fashionable and gentrified neighbourhood.
Runners will follow the Wall's course clockwise, and also pass through a rotunda near Checkpoint Charlie that houses a large panorama installation by artist Yadegar Asisi depicting daily life along the Wall in the 1980s.
By remembering Germany's painful division, "we can all help to ensure that this doesn't happen again, at least in Germany," said Eichner, for whom the Wall evokes the ongoing division of North and South Korea.
In all, 305 competitors from 24 countries are set to join, reflecting the growing popularity of such endurance contests that include the Ultra Trail du Mont Blanc and the notorious Badwater run in California's Death Valley.
The foreign contingent in Berlin, led by Japanese star Tsutomu Nagata, has doubled since last year and includes athletes from Australia, China, France, Italy, Spain, Turkey, the United States and Uruguay. Their ages range from 23 to 68 years for men and 21 to 73 for women.
German Peter Flock, 43, will seek to defend his win of last year, when he completed the run -- which is equivalent to almost four full marathons -- in 15 hours and 53 minutes.
As much as a journey along the historic scar through Berlin, the race will also be the culmination of months of training to endure the pain and extreme fatigue.
"We go through many ups and downs. We are also running with our heads," said Gaston Pruefer, 37, who met his wife Martina, 45, during the previous race.
Last year, he ran by her side to support her, day and night, before they crossed the finish line together.
The couple, who were born on either side of the Wall, believe that "history matters", but the two -- who now wear matching fluorescent clothes while they run -- get far more talkative when speaking about the future and the sporting challenge ahead.
They praised the Berlin race as an athletic "oasis", with its relatively gentle terrain, the favourable weather conditions expected and a network of 27 aid and catering stations along the way.