The Museum of Martyrdom "Under the Clock", a branch of the Lublin Museum in Lublin, was founded in 1979 on the initiative of the Club of former Political Prisoners of the Lublin Castle and "Under the Clock". In December 2017 it was open again after 2 years of renovation.
The museum’s exhibition is devoted to the history of prison in the Lublin Castle and the “House Under the Clock”. It contains a big collection of the correspondence (letters, kites, postcards) of the political prisoners of the Lublin Castle from the prison and concentration camps to which they were then sent (Auschwitz, Ravensbrück , Dachau, Sachsenhausen), the announcements and German decrees from the years 1939-1944. A different group consists of documents and personal memorabilia of former prisoners of the Castle (identity cards, school certificates, scout crosses, school badge, family photographs, notebooks and school textbooks) and a rich iconographic material of Lublin from the years 1939-1944, as well as the photographic archive of the former prisoners of the Castle from the years 1939-1954.