The prison at Berlin-Hohenschönhausen was operated by the Ministry for State Security (MfS)—more commonly known as the Stasi—beginning in 1951. East Germans who attempted to flee the GDR as well as thousands of political prisoners were held there. Prisoners were subjected to brutal interrogations, psychological torture, and lengthy incarceration, frequently in complete isolation. In the early 1990s, former prisoners initiated the establishment of a memorial and museum on the former site, the Hohenschönhausen Memorial. This photograph taken in 2009 shows a cell corridor in the former prison.