From the bend below the castle, Bouillon seems to hang between the rock and the river. The Semois, a slow, green stream, loops round the town in a tight horseshoe, and the old fortress stands on the ridge above, grey and square against the dark forest behind it. The bend is the sort of place where you cut the engine, because the sound of the water below and the smell of damp leaves and woodsmoke are part of the view.
The valley is a product of old geology. The Ardennes are the worn-down roots of a mountain range that was raised some three hundred million years ago, folded and compressed, and the Semois has cut through the hard schist and slate to make its meanders, leaving steep wooded flanks on one bank and gentler slopes on the other. The thin soil carries oak, beech and hazel, with wild boar and roe deer in the woods and kingfishers over the water. The valley is also known for its tobacco, grown here since the seventeenth century, and old drying sheds with slatted sides can be seen in the villages.
Riding in this area is a fine experience. The roads follow the river, rising and dropping across the spurs, with tight bends and steep little climbs, and each ridge brings a view of the next loop. The tarmac varies, and after wet weather the shaded stretches stay slippery with mud and leaves. In summer the villages are busy with canoeists and campers, and in autumn mist fills the valley in the morning. The border with France is only about a dozen kilometres away, and the old fortress town of Sedan, where Napoleon III surrendered in 1870 and where German armour broke through in 1940, is within easy reach.
Fuel is available in Bouillon, and it is wise to fill up in town, since the smaller villages along the river have no pumps. A cafe by the bridge is a pleasant place to look back at the castle. Come in May or October for the best colour and light, and bring a warm layer, as the valley holds the chill.