The case that will retain us in this presentation is probably still atypical in the wetland research landscape. Indeed, on the contrary of most of the work that considers the development of these areas in the In this section, we will consider the exploitation of wetlands in the context of a rural economy, or the exceptional aspect of certain sites that have sometimes become relics (such as the Marais Poitevin), we will consider the exploitation of wetlands in the context of a rural economy, or the exceptional aspect of certain sites that have sometimes become relics (such as the Marais Poitevin). urban. Through the study of the evolution of the wetlands of the urban periphery of Brussels between about 1100 and 1550, we hope to highlight several issues that intimately link urban history to the history of the marshes for many medieval and modern cities. This study is a first sketch, the ambition of which is to explore the new This is the path that makes some cities the "children of the swamp".