There are several parking spaces on the right-hand side by the stream after La Guillotière.
(S/E) Follow the stream along this dirt track, which is passable by vehicles but closed to traffic. Walk for about 900 m until you reach a weir.
(1) At this point, the vegetation makes the banks inaccessible. Take the path leading uphill to the left, reach a ruined hut and go round it on the right to reach a Fork in the road about twenty metres further on.
(2) Ignore the path that continues uphill and turn immediately downhill to the right to reach another Fork in the road.
(3) Turn off to your right. The path descends steeply towards the banks of the stream.
(4) Turn left to follow the banks of the Leysse for about 1,700 metres. This section is very damp, shaded and mossy. A few slippery patches might just give you a dip along the way.
(5) Continue to the left and climb for about a hundred metres until you reach the sign pointing towards the footbridge.
(6) Turn right to reach the Trou de l’Enfer footbridge, which is about 200 m away: take the time to go down and have a splash under the footbridge.
(7) To return, follow the same path back to the car park (S/E).