Hidden rooms (synonyms: secret spaces) are areas within a house or other structure that can only be accessed by hidden door. They may be bedrooms, studies, libraries, cult lairs, torture chambers, or other rooms. They may connect to the vents, to secret exits, or to the spaces between the walls. They may have peepholes into the main areas of the building with which a person could spy through.
When designing hidden rooms consider the reason for which they were constructed. They may have been built to hide a person, to hide an item or treasure, or to shield a secret activity from curious eyes.
Also consider how they fit into the floor plans of the building in which they exist. In narratives, clever characters may realize that the dimensions of a building, room, or space don’t make sense unless a hidden room is present.
There may be clues that a hidden room is nearby.