Denver International Airport, Colorado: Rumored underground tunnels and bunkers fuel conspiracy theories about secret societies and hidden government operations.
Cincinnati's Abandoned Subway, Ohio: America's largest ghost subway, never used and a hidden relic of ambitious urban plans gone awry.
Museum of the American Revolution, Philadelphia: Has a hidden passage that once led runaway slaves to freedom during the Underground Railroad era.
The Magic Castle, Los Angeles: A private club with hidden doors and secret passages, enhancing the mystique of its magic shows.
Prohibition Tunnels, Los Angeles: Hidden tunnels used during Prohibition to transport alcohol. Now echo with tales of Hollywood’s secretive past.
Speakeasy Tunnels, Chicago: Discreet tunnels once used by mobsters like Al Capone during Prohibition to smuggle alcohol and evade law enforcement.
Freemasons' Secret Passages, Boston: The Grand Lodge has concealed corridors, revealing Masonic history and traditions dating back centuries.
Underground City, Seattle: Subterranean passageways of the original Seattle before it was rebuilt on top after the 1889 fire.
Dupont Circle Tunnels, Washington, D.C.: Abandoned streetcar station with tunnels, now occasionally hosting art exhibits or unique events.