The Ijzer is the shortest of the three Belgian rivers. It is the only river in Belgium that flows into the sea. "Bachten de Kupe" (Behind the Wanne, ie Behind the Ijzer) is the West Flemish name for the area west of the Ijzer, which is bordered by the North Sea and the French border, or the "Schreve". When you get closer to Koksijde, you can see the highest dune on the Belgian coast, the Hoge Blekker, which glows from afar when the weather is sunny. Or, as the West Flemish put it, “bleach”. This is also the name of the 240 hectare nature reserve.