On the N slope of Roca Mur (La Màquina de Tren). From the road from Castellar del Vallès to Sant Llorenç Savall, shortly before reaching the latter village, a track leaves to the left and runs along the vall d'Horta; one kilometre before the Marquet de la Roca parking area there is a path that climbs in a S direction towards Roca Mur. Before that, a small col is reached and 150 metres further on, above the path, lies the pit, some 40 metres further west of the avenc gran de la Muntada.