Mentioned from 1329 onwards, the Château de Trois-Fontaines was altered many times over the centuries. A keep once stood on the site, of which only one wall remains today. Other buildings were later added to form an L-shaped castle. The rear stone façade dates from the 15th century, as does the great hall, which preserves a fine Gothic stone fireplace with capitals carved with human faces. As a forest prison, the castle served under the Ancien Régime as the headquarters of the gruyers, the forest hunting police. Poachers and wood thieves were thrown into its dungeon. The State purchased the property in 1906 in an attempt to preserve it. Restored between 1973 and 1976 by the non-profit Conseil de Trois-Fontaines, it hosted exhibitions on the Sonian Forest and its edges for 23 years. The property now belongs to Brussels Environment. Though today isolated by the urban fabric, the castle still offers an image of what the Brussels landscape may once have been, when forest surrounded the building. (Listed since 19/11/1986)