Czech Police Museum (Muzeum Policie České), Prague

In Communist times this was the rather formal Museum of the National Security Police, which focused on uncovering enemies of the socialist state. Now it is an extremely enlightening place to visit especially for those who can read the Czech exhibit labels (a one-page English text is also available). There are fascinating displays on notorious crimes of the past (with grisly photographs, e.g. that of a severed head in a suitcase) and a working machine that checks for counterfeit banknotes using ultra-violet light. A model of an old police station from the days of the Hapsburgs shows how things have changed. Enthusiasts will be enthralled by the handmade guns from the early twentieth century, made to fire anything from grenades to poison pellets.