Question: which landmark built on the site of a former city gate that marked the start of the road from Berlin to the town of Brandenburg an der Havel, is Frederick William II of Prussia responsible for?
Sentence (from "Brandenburg Euthanasia Centre"): The Brandenburg Euthanasia Centre (German: "NS-Tötungsanstalt Brandenburg" ), officially known as the Brandenburg an der Havel State Welfare Institute ("Landes-Pflegeanstalt Brandenburg a. H.") was established in 1939 and acted during the Nazi era as a killing centre as part of the Nazi Euthanasia Programme, subsequently referred to after the war as Action T4.
Relevant evidence: No