Blue House (Cheongwadae) Underground Tunnel

The supplied source is a general overview of 'underground city' concepts and does not provide site-specific details about any tunnel beneath or associated with the Blue House (Cheongwadae) in Seoul. No construction date, ownership history, incidents, access information, or documented uses tied to a Blue House tunnel are present in the provided material. The source outlines common functions of subterranean spaces—defensive refuge, transit, storage, habitation, drainage, and mausolea—but does not link those functions to a Blue House structure. Because the research notes contain only general information about underground places and no specifics for this site, any functional explanations for a presumed Blue House tunnel remain speculative and are marked as uncertain.