The Wabasha Street Caves are a series of man-made sandstone caves carved into the Mississippi River bluffs in the 1840s, originally used for cold storage. During Prohibition they housed the Castle Royal nightclub, frequented by some of the most notorious gangsters in America during the period when St. Paul was known as a sanctuary city for organised crime. The "St. Paul System" — a live-and-let-live arrangement between the police and criminal gangs — made the city unusually dangerous for its residents but peaceful in its public image.
Tours cover the caves' history, the gangster era, and the local legends associated with the tunnels. Ghost tours run on weekends. The site is in the West Side neighbourhood, across the river from downtown, with good views back toward the city centre.