My hometown Groningen has a couple of monuments strewn through the city. They appear without story or context as you wander through the streets. So you would need a local to tell you their secrets.
In my opinion this is the most special. It is an inconspicuous closed door. But the strange thing is that there is no handle. On closer inspection you might notice that it is full of scratches. Like those made by finger nails.
It is a second world monument which was carefully positioned accross my local synagogue. Although during the second world war some Jews were protected by the local populous a lot were deported as they couldn't find protection. This closed door is a symbol for those people since they couldn't find a way to escape. The door will remain forever closed to them.