Sønderborg’s Natløb is a Friday-in-September night run connected to the town’s Kulturnatten. The start and finish are by the Harbour Office on Nørrebro 1. Runners complete about 5.1 km through Sønderborg’s streets after dark. Walkers have a shorter route of about 2.5 km earlier in the evening. It is a large local participation event, drawing over 2,500 people for the run and walk. Participants must choose one route as the schedule does not permit doing both.
The walking route features Sønderborg Garden at the front, providing live music along the way. The run includes fast athletes finishing in under 20 minutes and participants in costumes who offer entertainment for spectators. A shared warm-up with a fitness instructor precedes each start. Prizes are awarded to the best-dressed individual and best-dressed team. The event expanded after its initial independent planning and subsequent joining of Kulturnatten, rapidly exceeding 2,240 participants and later setting a record of 2,569.