Between Les Brenets and Brémoncourt the Doubs River flows through Switzerland and generally forms the natural border with France along the way. A typical environment in the Doubs Nature Park consists of open woodland pastures alternating with forests, which looks like a mosaic. Over the centuries these areas were developed by livestock farming, horse breeding and forestry. At the northern edge of the plateau, the terrain steeply drops off to the Doubs. The river has formed gorges, some looking like canyons, and as it flows through the valley, it is gentle at times, wild at others. The natural value of this area lies in its exceptional diversity and it provides numerous rare habitats, such as floodplains, wildflower meadows, single trees, hedges, river banks, or the typical forests and woodland pastures mentioned before.

The tour begins at La Maison Monsieur. First you walk along the main road for a short while, before you cross the bridge near La Rasse and thus the border with France. Following the lovely path, you reach Biaufond and the lake of the same name with dozens of swans and ducks. As is typical for most river valleys in karst areas, the canyon offers a particular variety of habitats for flora and fauna: rocky cliffs, scree slopes, high and low water channels, river bends, islands, and backwaters. After Lac de Biaufond, the Doubs turns to the right. The hiking trail now continues uphill and climbs about 100 metres in altitude.

It takes at least three more hours to get to La Goule, followed shortly by the La Theusseret forest reserve. It was established in 1992 and at 89 hectares it is one of the ten largest in Switzerland. Nature is left to itself in the reserve. The wood is no longer utilised. Once you pass the power plant, this section of the trail ends in Goumois, after walking about 5 ½ hours. Part of the village is located in Switzerland, part in France. The Doubs forms the border between the two countries. Although the borders were established as far back as the Congress of Vienna, the two parts of the village have always shared their infrastructure. For example, the school is on Swiss land, while the church is located on the French side.