The Rubbenbruchsee Marathon is a modest December race held at Rubbenbruchsee near Osnabrück, taking place on the second Saturday of the month. The start and finish are located outside Café am See, directly by the water. The event maintains a low-key atmosphere with a restricted number of participants, a 6-hour cut-off, and the use of public paths shared with walkers. It appeals to runners seeking one final marathon before winter, or those using it as a consistent training benchmark before the upcoming season.
The course consists of nine laps around the lake, supplemented by seven additional loops through the adjacent forest, all on well-maintained, non-asphalt paths. This lap structure allows participants to repeatedly encounter the same points of interest, and spectators can see runners multiple times without extensive travel. RuM originated as a personal concept, and the event retains the character of a local get-together rather than a large-scale competition. Its unique elements and customs include collecting RuM medals, securing coveted starting positions, and a small incentive for returning participants.