The Courses Nature de la Baie d'Isigny feature two trail races starting from Isigny-sur-Mer in Normandy: Les Sentiers du Caramel at 10.5 km and Les “dix-huitres” Kilomètres du Caïeu at 17 km. Both begin at the town hall, with the 17 km race starting first, followed shortly by the 10.5 km. The Association des Marathoniens d'Isigny sur Mer organizes the event, which uses chip timing and limits the combined field to 700 runners.
The route consists of approximately 90% trails, crossing farmland, the coast, and the Norman bocage. Runners begin and end with a passage through the port of Isigny. They will use seaside dikes, polders, and country trails instead of a route heavy on roads. The 17 km race includes a cutoff at the 12 km mark; runners taking longer than 1 hour 25 minutes will not be classified. Prizes are awarded to the top three overall finishers and the first runner in each category. Participant prizes emphasize local products, including oysters, caramels, and Camembert from a town known for its butter and cheese production.