The Gorges du Doubs, about 20 km north of Porrentruy, are where the Doubs river cuts through the Jura limestone in a series of dramatic gorges and meanders along the Franco-Swiss border. The scenery is outstanding — towering cliffs, green water, and the extraordinary Saut du Doubs waterfall where the river drops 27 metres into a basin surrounded by forest.
The best approach from Porrentruy is to drive to Villers-le-Lac on the French side or Biaufond on the Swiss side, then take a boat excursion to the waterfall (the most popular option in summer) or walk the riverside trail. The gorges are at their most dramatic in spring when snowmelt swells the river. Well worth the detour if you are spending more than a day in the Ajoie.