In the hollow of the valleys of the Serre and Vilpion, this easy mountain bike route follows good tracks in the land of sugar beet. Marle, the economic engine between Laonnois and Thiérache, has an important architectural richness. After following the railway line, the discovery is enriched by the Romanesque church of Dercy and the massive water mill of Erlon. Half of the route, which can be split in two at Voyenne, is on flat ground.