From Mariembourg, where the Three Valleys steam train departs, you can reach Olloy-sur-Viroin near an old sandstone quarry. Follow the wooded foothills of the Ardennes towards Oignies-en-Thiérache, a former slate quarry village. After crossing the forest, you descend to the Ry de Rome dam, a magnificent stretch of water in the heart of the forest. At Couvin, you’ll reach the Eau Noire river, which shapes the whole town with its impressive cliff.