This memorial plaque at Metro-station Nollendorfplatz in <a href="//commons.wikimedia.org/wiki/Berlin-Sch%C3%B6neberg" title="Berlin-Schöneberg">Berlin-Schöneberg</a> is to commemorate the <a href="https://en.wikipedia.org/wiki/Pink_triangle" class="extiw" title="en:Pink triangle">en:Pink triangle</a>. It was one of the <a href="https://en.wikipedia.org/wiki/Nazi_concentration_camp_badges" class="extiw" title="en:Nazi concentration camp badges">en:Nazi concentration camp badges</a>, used by the German Nazis to identify male prisoners in concentration camps who were sent there because of their homosexuality.
<a href="//commons.wikimedia.org/wiki/User:Lienhard_Schulz" title="User:Lienhard Schulz">Lienhard Schulz</a>
CC BY 2.5
<span class="int-own-work" lang="en">Own work</span>