Fuhlsbüttel
Between 1933 and 1945, this was a Gestapo prison called Kola-Fu (Konzentrationslager Fuhlsbüttel). The prison was in an already existing prison and was for most prisoners a stop on the way to some other prison or concentration camp. In comparison with other and larger concentration camps, the number of prisoners and victims was significantly smaller, but this does not mean that the prisoners were treated differently than prisoners who were in larger concentration camps.
Current status: Preserved with museum (2008).
Address: Suhrenkamp 98, 22335 Hamburg.
Get there: Commuter train to Ohlsdorf Station.
Follow up in books: Browder, George C: Foundations of the Nazi police state – The Formation of the SS and SD (1989).
There is hardly any prison in Germany or the countries occupied by Germany that were not used by the Nazis for various purposes. I don’t know how many of them have any kind of museum or memorials, but in Germany, there is at least a moral demand from the outside world that some kind of memorial be established at virtually every place that can be linked to Nazism. The problem may be that it will be difficult to exclude any place because all places in Germany in one way or another have a connection to Nazi Germany.