Although it is just the prolongation of the first section of the Hartz-zuloa chamber, this area contains several interesting features . If we look at the walls we can see that certain areas have been blackened.

This colour is not due to any specific mineral but is the record of an enormous fire that raged in the Aralar range a few centuries ago. Records show that the area around Mendukilo was burnt to the ground and the ashes dissolved in water to filter into the cave.

This chamber also shows traces of the passing of humans: broken formations, remains of carbide (used to light the caves), etc.