Park next to the small water treatment plant on the edge of the D 635.
(S/E) Join the D 635, follow it to the right for about a hundred metres until you reach a small wooden sign by the side of the road. Turn left onto the fossil trail, which climbs slightly, and you will reach a three-way junction.
(1) Take the middle branch, keeping in the same direction. Continue for a good kilometre; just follow the well-maintained yellow markers.
(2) When you reach the main road at Salleneuve, turn right. Ignore the road on the left that leads to Perron and continue towards Portet. At the hamlet, turn left, go downhill for 100 metres and cross the road to find the path through the woods on the right, which is still marked by small wooden signs. Join the D 23.
(3) Follow it for about 100 metres, then take the path on the right that leads into the woods.
(4) At the crossroads, turn left.
(5) Turn left again to stay in the woods. You will come to a four-way junction.
(6) Continue straight ahead uphill.
(7) Turn right to descend towards the village of Aurignac, which you will reach via Chemin de la Bourdette. Turn right towards the town hall and join Rue Saint-Michel.
(8) Turn right, then right again a few dozen metres further on to go around the town hall and follow Rue du Château. Turn left to reach Avenue de l'Allée, cross it and take the narrow lane between the houses that leads to Avenue Boulogne. Cross at the pedestrian crossing and follow the avenue, turning right. Keep left at the three-way junction to reach the water treatment plant (S/E).