The marais audomarois is a living wetland of canals, drainage ditches, and market gardens that stretches north and east of Saint-Omer — a remarkably intact survival of a medieval agricultural landscape in the heart of industrial northern France. Farmers have worked these waterlogged fields from flat-bottomed barques for centuries, growing chicory, cauliflower, and other vegetables for the local and Lille markets.
The best way to see the marais is by boat: several operators near the town offer guided tours by electric barque along the canal network. You pass through tunnel-like corridors of willow and alder, between vegetable beds and small farmsteads, with herons standing motionless in the shallows. The marais is a UNESCO-designated wetland and a Ramsar site, and is one of the most atmospheric places in the Nord-Pas-de-Calais. Allow at least a half day.