Located at the font de les Bagasses, in the Terrades gorge. We will head S along the road shoulder for 80 metres, cross the road and find a steep ascending ramp with some steps that help with the climb (ETRS89 coordinates 324831 - 4655767); here begins the camí de Rúbies, which we will follow for approximately 1.85 metres. At this point (ETRS89 coordinates 325860 – 4655276) we will see the entrance of the cave called Mirador Nefer-Nefer hanging on the wall; to the left of it, but at the base of the cliff, a gully opens where the Pas de l'Osca is found. We will head towards it looking for the best passage; the cave is located inside the gully at 200 metres in a straight line and 78 metres higher up.