A barn church or barn chapel is a specific type of clandestine church, built in times that a certain church was illegal but tolerated as long as the churches were not specifically looking like churches.[1][2] These were no elaborate buildings but simple structures without pews. They were design to hold rather large kneeling and standing congregations.[3][4]
In rural areas those clandestine churches usually mimicked a barn, hence the name. In towns and cities people were more creative, hiding churches in houses and warehouses.