The streets of Madrid will only reveal so much about the true nature of the capital. Concealed beneath the manhole cover of the nearest sewer line is the gateway to a hidden realm below the surface. Here in the veiled and impenetrable darkness lies a vast labyrinth of subterranean galleries and tunnels – a perfectly devised system which controls the way the metropolis breathes. This netherworld defies the inexorable rhythm of days and nights in its role as the insomniac subconscious of the big city. That the world above appears to function entirely naturally is attributable to a system of heavy-duty engineering and technological advancement. This urbanistic, sci-fi documentary works with a sophisticated audiovisual composition, offering up an unconventional, contemplative viewing experience.