An old 17th-century pond in Belgian Lorraine gradually filled in, then was drained and planted with fir trees. In 1996 the municipality of Etalle bought part of the site (50 ha) with the help of the Walloon Region to turn the site back into anatural area. The preparation of and work on this site were organised as part of the Semois river contract. The aims of the restoration work are several and complementary and contribute to the valley's overall management (self-treatment of domestic effluents, flood control, enrichment of the flora and fauna, and development of the landscape's natural beauty). The first results seem fairly promising, for we are indeed witnessing a 'boom' in the site's biodiversity (birds, fish, insects, marsh plants, etc.). A water quality monitoring programme has been instituted to evaluate the processes that govern this aquatic ecosystem's functioning and periodic electrofishing has enabled us to monitor the development of the fish species that have moved in. One of the long-term stakes will be to design a balanced management programme for the area.