The Japanese city of Osaka has broken up what local authorities are calling the biggest – and possibly oldest – illegal gambling den they’ve encountered in years.

On Monday, Osaka Prefectural Police arrested 24 individuals after disrupting a major illegal baccarat casino operating out of a building in the Minami entertainment district. Police seized five gaming tables and ¥9m (US $80k) in cash, along with a further ¥200m ($1.8m) in cash in subsequent searches of buildings connected to the gambling operation.

The police officers who conducted Monday’s raid arrested the 41-year-old casino manager, who reportedly copped to operating the illegal gambling den, which ran 24 hours a day. In addition to the manager, police arrested nine casino employees and 14 gamblers. A further 26 staff and customers were questioned.

Police say the operation had elaborate security procedures, including a double-door guarding the entrance and 40 surveillance cameras located inside and outside the venue. The fourth-floor gaming den wasn’t directly accessible via elevator, meaning customers had to first alert casino staff, who would escort customers to floors above or below the casino, then lead them to their gambling promised land.