Mysterious Moscow, a dark subterranean world waiting to be explored, unknown to most surface dwellers, where old meets new in surprising ways. Volunteers navigate a labyrinth of underground rivers, tunnels and passages to discover hidden historic treasures and new subways under construction. They are the Moscow diggers. Each has his or her own motives and tasks when they descend into that urban underworld but they all share a true passion for exploration and the ambition to be the best in their unusual occupation.