Lum'Yerres is a night trail event starting from Yerres, a commune in Essonne south-east of Paris. It is an off-road running race, not a road event, with routes that range up to longer trail distances; one listed Trail XS option covers 22 km with about 700 meters of climbing.
The courses use the paths of La Grange state forest, so runners spend much of the race moving through woodland in the dark. The format suits trail runners who are comfortable with headlamps, uneven ground, and short but repeated climbs rather than people looking for a flat city run.