Mokotow Prison in Warsaw, also known as Rakowiecka Prison.

During the Stalinist years it was one of the best known prisons used by the secret police as a place of detention, torture and execution of the Polish political opposition and underground fighters. The prisoners, kept in tiny concrete cells in inhumane conditions, were subject to interrogation and prolonged physical torture. Many were executed and burried there.
In 1998 a memorial plaque was erected on the prison wall to commemorate the 283 known political prisoners executed on Rakowiecka Street between 1945 and 1955, as well as hundreds of others whose names and place of burial remain unknown.

Since 2016 it is under reconstruction to serve as a museum of political prisoners, and to be opend in 2019.

https://www.wikiwand.com/en/Mokot%C3%B3w_Prison