The Race takes place in Biel-Bienne (Siwtzerland) and is one of the oldest 100km events in the world,which began in 1959. The Ultra marathon is also a part of the European Ultramarathon Cup.
It event also includes a night marathon, half night marathon, Nordic walking. Its also possible to run the 100k in teams of 2 or 5 people.
The 100km is 1 big 100k loop and that the start is on 10pm (so you run through the night).
Click to reach the official site
Information about the event is available in : English French German