Exploring the S1 is a documentary that makes us to know an expedition to the heart of the Spanish Pyrenees to continue the exploration of one of the deepest cave systems in the world: Aranonera. S1 is the name of one entrance to the system, a way that leads us to great depths, but it represents much more than a door, is the legacy of decades of work and explorations. Exploring the S1 accompanies a team of cavers to explore unknown places, but the film goes beyond, it makes us to know the human aspects, also showing everything that we do not see often: the infrastructure and logistics that make this possible.—Anonymous