Hidden passageways are concealed corridors, tunnels, or other routes that can be used by those who know of their existence to escape, enter, or spy. Fictional hidden passageways are often concealed behind a hidden doorway, and may be crawlspaces, underground tunnels, or little known cave systems. They often lead to hidden rooms, secret chambers, or simply connect distant locations. Hidden passageways are used by assassins, spies, and people in the middle of realizing their newly purchased home contains a few dark secrets.

Hidden passages have a beginning, a route, and an end. Their beginnings often start with a hidden door, concealed trapdoor, or other secretive element. The routes they take may make use of tunnels, old sewer systems, crawlspaces, caves, or underground rivers.

Hidden passages that remain hidden are not as interesting. Consider who knows of them. There may be records of their existence in old architectural plans or dusty maps. Someone may have built the passage as an escape plan or found it while playing as a child.