A large 14x9.5 metre mouth which can only be accessed from inside through the train tunnel, since at the mouth we find the reservoir of the Herand weir.

From the mouth we find a gallery of 8.5 metres until reaching the wall that supports the backfill that was made to raise the train track, which is 2.6 metres higher. Once on top of the wall we find the train track and the end of the balma about 7 metres further on, on the right side we can access an upper level of the balma that allows us to reach the level of the mouth of the Balma but at 4.75 metres height with respect to the entrance.

At the mouth of the balma we find the reservoir of the Herand weir, and the weir in the Freser river prevents crossing it.

We must cross the Cabreta bridge and follow the path that climbs past the old carbide factory; just as we cross the small canal tunnel, in front of us we find a small path that we must follow for a while, and wherever we can, passing through the middle of the forest, we will go down until we find the train track, following the track in a N direction until seeing the tunnel that passes inside the balma. We must be alert with the trains, since they never pass at the time they should.