Berlin-Hohenschönhausen Stasi Prison Complex Museum, Lichtenberg, Berlin, Germany

A suggested reason why the torture of East Germany's own citizenry was permitted for so long was Hohenschönhausen exclusion zone. The prison was located in a large restricted area bordered by a large military town. Additionally, it officially did not exist during many of the year it operated, being left off all maps. These two measures combined meant that few people who did not work there know what occurred inside. Because it was not well known, the prison was not stormed by demonstrators after the fall of the Wall. This allowed prison authorities to destroy much of the evidence of their crimes. Today, much of our knowledge comes from former prisoners personal accounts and documentation from other GDR institutions.
Memorial
The Hohenschönhausen Memorial (Gedenkstätte) was founded in the early 1990s by former inmates. The prison was listed as a historical site in 1992 and welcomed its first visitors in 1994. The Foundation is funded equally by both the German federal government and the Berlin state government.