Officially called the National Museum of Organized Crime and Law Enforcement, the Mob Museum is housed in the 1933 former federal courthouse — itself a piece of the story it tells, since one of the famous Kefauver hearings on organised crime took place in this very building. Three floors trace organised crime from Prohibition through modern transnational cartels, with strong emphasis on the mob's role in building Las Vegas.
Real artefacts make the displays land: a section of the actual St Valentine's Day Massacre wall, mug shots, weapons, surveillance equipment, and a recreated execution chamber. The basement holds a working speakeasy and a distillery you can tour. Allow two to three hours; it is one of the few Vegas museums that genuinely rewards a slow visit.